Bump kotlin_version from 1.4.30 to 1.4.31

Bumps `kotlin_version` from 1.4.30 to 1.4.31.

Updates `kotlin-gradle-plugin` from 1.4.30 to 1.4.31
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v1.4.31/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.4.30...v1.4.31)

Updates `kotlin-stdlib-jdk7` from 1.4.30 to 1.4.31
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v1.4.31/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.4.30...v1.4.31)

Updates `kotlin-stdlib` from 1.4.30 to 1.4.31
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v1.4.31/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.4.30...v1.4.31)

Signed-off-by: dependabot[bot] <[email protected]>

build.gradle

@@ -1,7 +1,7 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.4.30'
+    ext.kotlin_version = '1.4.31'
     repositories {
         google()
         jcenter()