Merge pull request #7636 from nextcloud/dependabot/gradle/kotlin_version-1.4.21

Bump kotlin_version from 1.4.20 to 1.4.21

build.gradle

@@ -8,7 +8,7 @@ import com.github.spotbugs.snom.SpotBugsTask
 // its root folder, another one for the app module in subfolder of root.
 
 buildscript {
-    ext.kotlin_version = '1.4.20'
+    ext.kotlin_version = '1.4.21'
     repositories {
         google()
         jcenter()