Bump org.jetbrains.kotlin:kotlin-gradle-plugin from 1.8.20 to 1.8.21 (#608)

Bumps [org.jetbrains.kotlin:kotlin-gradle-plugin](https://github.com/JetBrains/kotlin) from 1.8.20 to 1.8.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.8.20...v1.8.21)

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

Author: dependabot[bot]

build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.8.20'
+    ext.kotlin_version = '1.8.21'
     repositories {
         maven {
             url "https://plugins.gradle.org/m2/"

bundles/sirix-kotlin-api/build.gradle

@@ -6,7 +6,7 @@ buildscript {
     }
 
     dependencies {
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.20"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.21"
     }
 }
 

bundles/sirix-rest-api/build.gradle

@@ -4,7 +4,7 @@ buildscript {
     }
 
     dependencies {
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.20"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.21"
         classpath "com.avast.gradle:gradle-docker-compose-plugin:0.14.5"
         //classpath "org.jetbrains.dokka:dokka-gradle-plugin:0.10.0"
     }