le_audio: Don't clear sink metadata context on monitor mode change

Remove redundant metadata context clearance when disabling monitor mode.

Bug: 349310336
Bug: 381054654
Test: atest bluetooth_le_audio_client_test
Flag: com::android::bluetooth::flags::leaudio_use_audio_recording_listener
Change-Id: Ia33c61825d6e8d772b5d1be650dabe19a4aa07f4