BluetoothMidiService: remove accidental versions in XML

Some android:version statements accidentally got introduced
when adding some tests. This caused problems for some OEMs
when testing.

Bug: 160079599
Test: atest BluetoothMidiTests
Test: https://source.android.com/devices/audio/midi_test.html#bluetooth_le_test
Change-Id: I2f7313390a27f45f01e82af373da278401448ad8