build(deps): bump org.jetbrains.kotlin:kotlin-gradle-plugin

Bumps [org.jetbrains.kotlin:kotlin-gradle-plugin](https://github.com/JetBrains/kotlin) 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)

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

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

buildSrc/build.gradle.kts

@@ -17,5 +17,5 @@ repositories {
 
 dependencies {
     implementation("io.gitlab.arturbosch.detekt:detekt-gradle-plugin:1.23.7")
-    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:2.0.20")
+    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:2.0.21")
 }