Merge pull request #1644 from austinhuang0131/renovate/org.jetbrains.kotlin-kotlin-gradle-plugin-1.x

Update dependency org.jetbrains.kotlin:kotlin-gradle-plugin to v1.5.21

build.gradle

@@ -1,6 +1,6 @@
 buildscript {
     ext{
-        kotlin_version = '1.5.20'
+        kotlin_version = '1.5.21'
         nav_version = "2.4.0-alpha04"
     }