Remove assert I accidentally left in (I meant to remove it when I re-added the defensive check above).

packages/firestore/CHANGELOG.md

@@ -1,7 +1,7 @@
 # Unreleased
-- [fixed] Fixed a regression in the Firebase JS release 4.11.0 that could 
-  cause a crash if a user signs out while the client is offline, resulting in 
-  an error of "Attempted to schedule multiple operations with timer id 
+- [fixed] Fixed a regression in the Firebase JS release 4.11.0 that could
+  cause a crash if a user signs out while the client is offline, resulting in
+  an error of "Attempted to schedule multiple operations with timer id
   listen_stream_connection_backoff".
 
 # 0.3.5

packages/firestore/src/remote/persistent_stream.ts

@@ -472,11 +472,6 @@ export abstract class PersistentStream<
         return;
       }
 
-      assert(
-        this.state === PersistentStreamState.Backoff,
-        'Backoff should have been canceled if we left the Backoff state.'
-      );
-
       this.state = PersistentStreamState.Initial;
       this.start(listener);
       assert(this.isStarted(), 'PersistentStream should have started');