build: update tools

Change-Id: Ic7491b8a0a3c6a088eec954a018823da9af35142

ring-android/build.gradle

@@ -5,7 +5,7 @@ buildscript {
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.2.0-rc01'
+        classpath 'com.android.tools.build:gradle:4.2.0'
         classpath 'com.google.gms:google-services:4.3.5'
     }
 }