Bump org.jetbrains.kotlin:kotlin-gradle-plugin from 2.0.21 to 2.1.21

Bumps [org.jetbrains.kotlin:kotlin-gradle-plugin](https://github.com/JetBrains/kotlin) from 2.0.21 to 2.1.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.21...v2.1.21)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-gradle-plugin
  dependency-version: 2.1.21
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

buildSrc/build.gradle.kts

@@ -9,7 +9,7 @@ repositories {
 
 
 dependencies {
-    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:2.0.21")
+    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.21")
     implementation("org.jetbrains.kotlin:kotlin-serialization:2.0.21")
     implementation("com.diffplug.spotless:spotless-plugin-gradle:6.25.0")
 }