Update dependency org.jetbrains.kotlin:kotlin-test-junit to v2.3.20 (#131)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

backend/gradle/libs.versions.toml

@@ -7,7 +7,7 @@ detekt = "1.23.8"
 gradle_versions_filter = "0.1.16"
 kotest = "6.1.7"
 kotlin_logging = "8.0.01"
-kotlin = "2.3.10"
+kotlin = "2.3.20"
 kotlinter = "5.4.2"
 kotlinx_coroutines = "1.10.2"
 kotlinx_serialization = "1.10.0"