Ad Clicked fix, Android link error. (#735)

Updated dependencies to support new AdClicked callback interface.

Author: DellaBitta

admob/admob_resources/build.gradle

@@ -46,7 +46,7 @@ android {
 
 dependencies {
   implementation 'com.google.firebase:firebase-analytics:19.0.0'
-  implementation 'com.google.firebase:firebase-ads:20.1.0'
+  implementation 'com.google.firebase:firebase-ads:20.4.0'
 }
 
 afterEvaluate {

admob/src_java/com/google/firebase/admob/internal/cpp/InterstitialAdHelper.java

@@ -217,7 +217,8 @@ public void run() {
   private class InterstitialAdFullScreenContentListener
       extends FullScreenContentCallback implements OnPaidEventListener {
 
-    public void onAdClicked() {
+    @Override
+    public void onAdClicked () {
       synchronized (mInterstitialLock) {
         notifyAdClickedFullScreenContentEvent(mInterstitialAdInternalPtr);
       }

release_build_files/Android/firebase_dependencies.gradle

@@ -17,7 +17,7 @@ import org.gradle.util.ConfigureUtil;
 // A map of library to the dependencies that need to be added for it.
 def firebaseDependenciesMap = [
   'app' : ['com.google.firebase:firebase-analytics:19.0.0'],
-  'admob' : ['com.google.firebase:firebase-ads:19.8.0',
+  'admob' : ['com.google.firebase:firebase-ads:20.4.0',
              'com.google.firebase:firebase-analytics:19.0.0',
              'com.google.android.gms:play-services-base:17.6.0'],
   'analytics' : ['com.google.firebase:firebase-analytics:19.0.0',