Bump kotlin.version from 2.0.20 to 2.0.21 in /p3c-pmd

Bumps `kotlin.version` from 2.0.20 to 2.0.21.

Updates `org.jetbrains.kotlin:kotlin-stdlib-jdk8` from 2.0.20 to 2.0.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.0.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.20...v2.0.21)

Updates `org.jetbrains.kotlin:kotlin-maven-plugin` from 2.0.20 to 2.0.21

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-stdlib-jdk8
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin:kotlin-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

p3c-pmd/pom.xml

@@ -24,7 +24,7 @@
         <!--libraries versions-->
         <pmd.version>6.55.0</pmd.version>
         <annotation.version>1.3.2</annotation.version>
-        <kotlin.version>2.0.20</kotlin.version>
+        <kotlin.version>2.0.21</kotlin.version>
         <x8l.version>2.3.9</x8l.version>
         <commons-lang3.version>3.17.0</commons-lang3.version>
         <commons-io.version>2.17.0</commons-io.version>