Bump kotlin-gradle-plugin from 1.6.10 to 1.6.21 (#42)

Bumps [kotlin-gradle-plugin](https://github.com/JetBrains/kotlin) from 1.6.10 to 1.6.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v1.6.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.6.10...v1.6.21)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-gradle-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

build.gradle

@@ -5,7 +5,7 @@ buildscript {
     }
     dependencies {
         classpath("com.android.tools.build:gradle:7.0.3")
-        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.10")
+        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.21")
         classpath("com.github.dcendents:android-maven-gradle-plugin:2.1")
     }
 }