leaudio-ubuntu: Restrict central device to LE support only

This will simplify connection to the peripheral device.
In this case PipeWire/WirePlumber should only register the LC3 codec as the
A2DP codecs registration is not possible and BlueZ daemon will reject all
codecs if one is not allowed.

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>