build(deps): bump kotlin.version from 1.9.20 to 1.9.21 (#2241)

Bumps `kotlin.version` from 1.9.20 to 1.9.21.

Updates `org.jetbrains.kotlin:kotlin-stdlib-jdk8` from 1.9.20 to 1.9.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.9.20...v1.9.21)

Updates `org.jetbrains.kotlin:kotlin-reflect` from 1.9.20 to 1.9.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.9.20...v1.9.21)

Updates `org.jetbrains.kotlin:kotlin-maven-plugin` from 1.9.20 to 1.9.21

---
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-reflect
  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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

kotlin/pom.xml

@@ -29,7 +29,7 @@
 
   <properties>
     <main.basedir>${project.basedir}/..</main.basedir>
-    <kotlin.version>1.9.20</kotlin.version>
+    <kotlin.version>1.9.21</kotlin.version>
     <kotlinx.coroutines.version>1.7.3</kotlinx.coroutines.version>
   </properties>