Remove unused disposable

app/src/main/java/org/mercury_im/messenger/android/ui/chat/ChatActivity.java

@@ -34,7 +34,6 @@ public class ChatActivity extends AppCompatActivity
     public static final String EXTRA_CHAT_ID = "CHAT_ID";
 
     private final MessagesRecyclerViewAdapter recyclerViewAdapter = new MessagesRecyclerViewAdapter();
-    private final CompositeDisposable disposable = new CompositeDisposable();
 
     @BindView(R.id.toolbar)
     Toolbar toolbar;
@@ -89,11 +88,6 @@ public class ChatActivity extends AppCompatActivity
         });
     }
 
-    public void onStop() {
-        super.onStop();
-        disposable.clear();
-    }
-
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.