Bump kotlinVersion from 2.0.21 to 2.2.20

Bumps `kotlinVersion` from 2.0.21 to 2.2.20.

Updates `org.jetbrains.kotlin:kotlin-gradle-plugin` from 2.0.21 to 2.2.20
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.21...v2.2.20)

Updates `org.jetbrains.kotlin:kotlin-allopen` from 2.0.21 to 2.2.20
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.21...v2.2.20)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-gradle-plugin
  dependency-version: 2.2.20
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-allopen
  dependency-version: 2.2.20
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

buildSrc/build.gradle.kts

@@ -14,7 +14,7 @@ dependencies {
     implementation("de.thetaphi:forbiddenapis:3.9")
     implementation("com.github.spotbugs.snom:spotbugs-gradle-plugin:6.1.13")
     implementation("org.gradle:test-retry-gradle-plugin:1.6.2")
-    val kotlinVersion = "2.0.21"
+    val kotlinVersion = "2.2.20"
     implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")
     implementation("org.jetbrains.kotlin:kotlin-allopen:$kotlinVersion")
     implementation(libs.detekt)