leaudio: Don't adjust metadata when choosing configuration

Le audio code maintain configuration_context_type_ and
metadata_context_types_.
The configuration_context_type_ is choosen based on the
metadata_context_types_, which contains a list of all the mixed streams.
This patch fixes that.

Bug: 251803434
Test: atest BluetoothInstrumentationTests
Test manual: Media stream + notification - make sure configuratin is not
changed
Tag: #feature

Change-Id: Icc5b134abe39170882705a0f0bb261eb300eaf76