Fix formatting

Author: Rachel Prince

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

@@ -31,7 +31,6 @@
 import androidx.annotation.VisibleForTesting;
 import androidx.browser.customtabs.CustomTabsIntent;
 import com.google.android.gms.common.internal.Preconditions;
-import com.google.android.gms.tasks.CancellationToken;
 import com.google.android.gms.tasks.CancellationTokenSource;
 import com.google.android.gms.tasks.OnFailureListener;
 import com.google.android.gms.tasks.OnSuccessListener;