Add RECEIVER_NOT_EXPORTED to TV PiP broadcast receiver

Not explicitly adding this flag causes a SecurityException when PiP is
entered.

Bug: 269101156
Test: manual - start a PiP -> no crash, double press home -> PiP menu opens, click on PiP notificaation -> PiP goes back to fullscreen

Change-Id: I3c1f657de191343f3a33d3f4a9cf13467ff83f4b