Make infoText CharSequence non null

Author: lfkellogg

firebase-appdistribution-api/api.txt

@@ -20,7 +20,7 @@ package com.google.firebase.appdistribution {
     method @NonNull public com.google.android.gms.tasks.Task<java.lang.Void> signInTester();
     method public void signOutTester();
     method public void startFeedback(int);
-    method public void startFeedback(CharSequence);
+    method public void startFeedback(@NonNull CharSequence);
     method @NonNull public com.google.firebase.appdistribution.UpdateTask updateApp();
     method @NonNull public com.google.firebase.appdistribution.UpdateTask updateIfNewReleaseAvailable();
   }

firebase-appdistribution-api/src/main/java/com/google/firebase/appdistribution/FirebaseAppDistribution.java

@@ -139,7 +139,7 @@ public interface FirebaseAppDistribution {
    * @param infoText text to display to the tester before collecting feedback data (e.g. Terms and
    *     Conditions)
    */
-  void startFeedback(CharSequence infoText);
+  void startFeedback(@NonNull CharSequence infoText);
 
   /** Gets the singleton {@link FirebaseAppDistribution} instance. */
   @NonNull