Bump kotlinVersion from 1.4.21 to 1.4.30 (#552)

Bumps `kotlinVersion` from 1.4.21 to 1.4.30.

Updates `kotlin-gradle-plugin` 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](JetBrains/kotlin@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](JetBrains/kotlin@v1.4.21...v1.4.30)

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

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

build.gradle

@@ -1,6 +1,6 @@
 buildscript {
     ext {
-        kotlinVersion = '1.4.21'
+        kotlinVersion = '1.4.30'
         androidGradleVersion = '4.1.2'
         coroutineVersion = '1.4.2'