Revert "Update navigator on pen-up."

This reverts commit 7065131c267fd34c917e68dd7ab5781ebad79528.
Remove delayed navigator updating

Navigator now updates in real time.
Delayed update seemed to cause more problems than it solved. Overriding
the updateScene() slot triggers a different codepath in QGraphicsScene which
appears to cause items outside the scene rectangle to not update properly.
Fix navigator focus rect refreshing