Merge pull request #2978 from nextcloud/dependabot/gradle/kotlinVersion-1.8.21

Build(deps): Bump kotlinVersion from 1.8.20 to 1.8.21

build.gradle

@@ -24,7 +24,7 @@
 buildscript {
 
     ext {
-        kotlinVersion = '1.8.20'
+        kotlinVersion = '1.8.21'
     }
 
     repositories {