changing the visbility of the internal constructor

Author: pranavrajgopal

firebase-app-distribution/src/main/java/com/google/firebase/appdistribution/FirebaseAppDistribution.java

@@ -70,8 +70,9 @@ public class FirebaseAppDistribution implements Application.ActivityLifecycleCal
  private CancellationTokenSource checkForUpdateCancellationSource;
  private final Executor checkForUpdateExecutor;
 
- /** Constructor for FirebaseAppDistribution */
- public FirebaseAppDistribution(
+ /** Internal Constructor for FirebaseAppDistribution */
+ @VisibleForTesting
+ FirebaseAppDistribution(
  @NonNull FirebaseApp firebaseApp,
  @NonNull FirebaseInstallationsApi firebaseInstallationsApi,
  @NonNull FirebaseAppDistributionTesterApiClient firebaseAppDistributionTesterApiClient) {