Remove add slippery flag to nav bar when connected to launcher service

Added a listener for OverviewProxyService to get updates when the
service is connected to the launcher so that the nav bar can toggle the
slippery flag to allow more touch inputs after dragging out of the it.

Bug: 67957962
Test: manual
Change-Id: Ib1ebaec318252021fa986ec554136f19d61126f8