Bump kotlin.version from 1.6.20 to 1.6.21 (#451)

Bumps `kotlin.version` from 1.6.20 to 1.6.21.

Updates `kotlin-bom` from 1.6.20 to 1.6.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v1.6.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.6.20...v1.6.21)

Updates `kotlin-maven-plugin` from 1.6.20 to 1.6.21

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-bom
  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] <support@github.com>

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

pom.xml

@@ -39,7 +39,7 @@
     <junit.version>4.13.2</junit.version>
     <kotlin-logging.version>2.1.21</kotlin-logging.version>
     <kotlin.compiler.jvmTarget>${java.target.version}</kotlin.compiler.jvmTarget>
-    <kotlin.version>1.6.20</kotlin.version>
+    <kotlin.version>1.6.21</kotlin.version>
     <ktlint-maven-plugin.version>1.13.0</ktlint-maven-plugin.version>
     <license-maven-plugin.version>2.0.0</license-maven-plugin.version>
     <logback-classic.version>1.2.11</logback-classic.version>