Remove spammy logging in LocalMediaManager

Both conditions that trigger this logging are spurious:
- getMutingExpectedDevice returning null is the norm. It will return
  non-null only when SASS is in effect.
- mBluetoothAdapter being null is already being logged elsewhere. For
  example, in buildDisconnectedBluetoothDevice.

So, no need to log neither condition. Particularly not as warnings.

Bug: b/328537710
Change-Id: I1d978a34350c1d3fef36fe275cf014b58993bac4
Test: Presubmit. Trivially safe change.