Update build.gradle to use default Build Tools (30.0.2) required by Android Gradle Plugin 4.2.0 (#2064)

jme3-android-examples/build.gradle

@@ -2,7 +2,7 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 28
-    buildToolsVersion "28.0.3"
+    buildToolsVersion "30.0.2"
 
     lintOptions {
         // Fix nifty gui referencing "java.awt" package.