Remove the unbonded device from mDeviceGroupIdMap

We should remove the device key from mDeviceGroupIdMap as the device
bond state change to unbond. As the user enter the device into the
pairing mode, the setting would not based on the previous information to
group the devices before bonding.

Bug: 226785322
Test: unpair the device, and put the set into pairing mode, check the UI
could show both devices

Change-Id: I53eaee4261a0f0f0af42c65255589f8e8a4c259d