Revert "a2dp: Set the default A2DP bitrate to high quality"

This reverts commit ce6c2405a9272656285019754fd4d4ac223b92bd.
Revert "Bluetooth: Change Sampling Frequency to 48 kHz"

This reverts commit 69f86c8d0f1f2d1adfd04f94bfd4580a3bc61d4c.