Remove outdated emulator check which causes BT to not start

ro.kernel.qemu based check to determine whether Bluetooth should be
started or not was an old hack used when "features" was not available to
determine hardware availability. This was later fixed with the
hasSystemFeature check. However, the old check was not removed.

The presence of the old check causes Bluetooth to not start on Android
Things devices which have ro.kernel.qemu set for graphics usage. It's
also preferable to depend on the system API rather than on build
configs. Related CLs modify the emulator builds to correct the config in
builds.

Bug: 35361545
Change-Id: I219ce5e14709c76dcba43af4693093e985269d43
Test: Verified by launching bluetooth on local devices after removing
the old check. Also verified by booting up the emulator and verifying
that Bluetooth Services do not start.