Bump kotlin_version from 1.4.21 to 1.4.30

Bumps `kotlin_version` from 1.4.21 to 1.4.30.

Updates `kotlin-gradle-plugin` from 1.4.21 to 1.4.30

Updates `kotlin-stdlib-jdk7` from 1.4.21 to 1.4.30
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](https://github.com/JetBrains/kotlin/compare/v1.4.21...v1.4.30)

Updates `kotlin-stdlib` from 1.4.21 to 1.4.30
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](https://github.com/JetBrains/kotlin/compare/v1.4.21...v1.4.30)

Signed-off-by: dependabot[bot] <support@github.com>

build.gradle

@@ -2,7 +2,7 @@
 
 buildscript {
     // Ref: https://kotlinlang.org/releases.html
-    ext.kotlin_version = '1.4.21'
+    ext.kotlin_version = '1.4.30'
     ext.kotlin_coroutines_version = "1.4.1"
     repositories {
         google()