Remove m_stopEventsToIgnore

6.6.0 and 7.0.0 mm-renderer don't appear to produce spurious stopped
state updates.  From the MMR_STOPPED in one of the comments, it looks
like this was a problem with the BlackBerry mm-renderer.

Change-Id: Ia336195b48df342c376b7fb3c8eb2a65ef748032
Reviewed-by: Christian Stromme <christian.stromme@qt.io>