The ng_h4 module was disconnected 13 years ago when the tty later was
locked by Ed. It completely fails to compile, and has a number of false
positives for Giant use. Remove it for lack of interest. Bluetooth has
largely (completely?) moved on from bluetooth over UART transport.

OK'd by:		emax
Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D31846