leaudio: Do not update metadata if not needed

In case remote device removes some available context types, code should
do double check on metadata which are about to send in update. Otherwise
we mind end up sending same metadata which is reduntant.

Bug: 296830689
Test: atest bluetooth_le_audio_test
Tag: #feature

Change-Id: I858edeaae54f477ce23aee917caf6b6449f3a0bf