Revert "MediaRouter: Add SystemMediaRoute2Provider to publish default route"

This reverts commit cfa8f9ab6181d4c9c32da4d1ea769f1be6655072.

Reason for revert: Breaking apct/bluetooth/instrumentation_test
Bug: 144755565

Change-Id: If988041a2478cff3b69ea7b8885a35b86e6c3053
5 files changed