Bump log4j.version from 2.13.3 to 2.15.0

Bumps `log4j.version` from 2.13.3 to 2.15.0.

Updates `log4j-core` from 2.13.3 to 2.15.0

Updates `log4j-slf4j-impl` from 2.13.3 to 2.15.0

Updates `log4j-jul` from 2.13.3 to 2.15.0

---
updated-dependencies:
- dependency-name: org.apache.logging.log4j:log4j-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.logging.log4j:log4j-slf4j-impl
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.logging.log4j:log4j-jul
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pom.xml

@@ -89,7 +89,7 @@
         <packageVersion.dir>com/staffbase/plugins/sdk</packageVersion.dir>
         <packageVersion.package>${project.groupId}.json</packageVersion.package>
         <jose4j.version>0.7.2</jose4j.version>
-        <log4j.version>2.13.3</log4j.version>
+        <log4j.version>2.15.0</log4j.version>
         <junit.version>4.13</junit.version>
         <mockito.version>3.5.2</mockito.version>
     </properties>