Remove assert on StubVoicemailClient.addActivationStateListener()

The default "do nothing" behavior is enough.

Bug: 69309850
Test: N/A
PiperOrigin-RevId: 176427193
Change-Id: Icd66f8ebb75b889a3cceef895bc3bf71c466ccf6
diff --git a/java/com/android/voicemail/stub/StubVoicemailClient.java b/java/com/android/voicemail/stub/StubVoicemailClient.java
index 3069ea4..2b02261 100644
--- a/java/com/android/voicemail/stub/StubVoicemailClient.java
+++ b/java/com/android/voicemail/stub/StubVoicemailClient.java
@@ -111,12 +111,12 @@
 
   @Override
   public void addActivationStateListener(ActivationStateListener listener) {
-    throw Assert.createAssertionFailException("should never be called on stub.");
+    // Do nothing
   }
 
   @Override
   public void removeActivationStateListener(ActivationStateListener listener) {
-    throw Assert.createAssertionFailException("should never be called on stub.");
+    // Do nothing
   }
 
   @Override