Update kotlin to v2.4.21

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
org.jetbrains.kotlin.jvm	2.4.10 → 2.4.21
org.jetbrains.kotlin.plugin.jpa	2.4.10 → 2.4.21

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
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The artifact failure details are included below:

File name: gradle/libs.versions.toml

Command failed: ./gradlew -Dorg.gradle.jvmargs=-Xms512m -Xmx512m --console=plain --dependency-verification lenient -q --write-verification-metadata sha256 dependencies

FAILURE: Build completed with 3 failures.

1: Task failed with an exception.
-----------
* Where:
Build file '/tmp/renovate/repos/github/accrescent/server/testdata/android-app-low-target-sdk/build.gradle.kts' line: 55

* What went wrong:
Error resolving plugin [id: 'com.android.application', version: '9.3.1']
> A problem occurred configuring project ':build-logic'.
   > Could not resolve all artifacts for configuration 'classpath'.
      > Could not resolve org.jetbrains.kotlin:kotlin-stdlib:2.3.21.
        Required by:
            buildscript of project ':build-logic'
            buildscript of project ':build-logic' > org.gradle.kotlin.kotlin-dsl:org.gradle.kotlin.kotlin-dsl.gradle.plugin:6.6.4 > org.gradle.kotlin:gradle-kotlin-dsl-plugins:6.6.4
         > Repository Gradle Central Plugin Repository is disabled due to earlier error below:
            > Could not resolve org.jetbrains.kotlin:kotlin-gradle-plugins-bom:2.3.21.
               > Could not get resource 'https://plugins.gradle.org/m2/org/jetbrains/kotlin/kotlin-gradle-plugins-bom/2.3.21/kotlin-gradle-plugins-bom-2.3.21.pom'.
                  > Could not GET 'https://repo.maven.apache.org/maven2/org/jetbrains/kotlin/kotlin-gradle-plugins-bom/2.3.21/kotlin-gradle-plugins-bom-2.3.21.pom'. Received status code 429 from server: Too Many Requests
> There are 4 more failures with identical causes.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights from a Build Scan (powered by Develocity).
> Get more help at https://help.gradle.org.
==============================================================================

2: Task failed with an exception.
-----------
* What went wrong:
A problem occurred configuring project ':build-logic'.
> Could not resolve all artifacts for configuration 'classpath'.
   > Could not resolve org.jetbrains.kotlin:kotlin-stdlib:2.3.21.
     Required by:
         buildscript of project ':build-logic'
         buildscript of project ':build-logic' > org.gradle.kotlin.kotlin-dsl:org.gradle.kotlin.kotlin-dsl.gradle.plugin:6.6.4 > org.gradle.kotlin:gradle-kotlin-dsl-plugins:6.6.4
      > Repository Gradle Central Plugin Repository is disabled due to earlier error below:
         > Could not resolve org.jetbrains.kotlin:kotlin-gradle-plugins-bom:2.3.21.
            > Could not get resource 'https://plugins.gradle.org/m2/org/jetbrains/kotlin/kotlin-gradle-plugins-bom/2.3.21/kotlin-gradle-plugins-bom-2.3.21.pom'.
               > Could not GET 'https://repo.maven.apache.org/maven2/org/jetbrains/kotlin/kotlin-gradle-plugins-bom/2.3.21/kotlin-gradle-plugins-bom-2.3.21.pom'. Received status code 429 from server: Too Many Requests
> There are 4 more failures with identical causes.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights from a Build Scan (powered by Develocity).
> Get more help at https://help.gradle.org.
==============================================================================

3: Task failed with an exception.
-----------
* Where:
Build file '/tmp/renovate/repos/github/accrescent/server/testdata/android-app-low-target-sdk/build.gradle.kts' line: 55

* What went wrong:
Error resolving plugin [id: 'com.android.application', version: '9.3.1']
> A problem occurred configuring project ':build-logic'.
   > Could not resolve all artifacts for configuration 'classpath'.
      > Could not resolve org.jetbrains.kotlin:kotlin-stdlib:2.3.21.
        Required by:
            buildscript of project ':build-logic'
            buildscript of project ':build-logic' > org.gradle.kotlin.kotlin-dsl:org.gradle.kotlin.kotlin-dsl.gradle.plugin:6.6.4 > org.gradle.kotlin:gradle-kotlin-dsl-plugins:6.6.4
         > Repository Gradle Central Plugin Repository is disabled due to earlier error below:
            > Could not resolve org.jetbrains.kotlin:kotlin-gradle-plugins-bom:2.3.21.
               > Could not get resource 'https://plugins.gradle.org/m2/org/jetbrains/kotlin/kotlin-gradle-plugins-bom/2.3.21/kotlin-gradle-plugins-bom-2.3.21.pom'.
                  > Could not GET 'https://repo.maven.apache.org/maven2/org/jetbrains/kotlin/kotlin-gradle-plugins-bom/2.3.21/kotlin-gradle-plugins-bom-2.3.21.pom'. Received status code 429 from server: Too Many Requests
> There are 4 more failures with identical causes.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights from a Build Scan (powered by Develocity).
> Get more help at https://help.gradle.org.
==============================================================================

BUILD FAILED in 1m 3s