bluetooth: fix comment in bluetooth.device.conf

The default for discoverable is 'NO' not 'YES'. This now matches the man
page.

Event: Advanced UNIX Programming Course (Fall'23) at NTHU.
Reviewed by: imp, zlei
Pull Request: https://github.com/freebsd/freebsd-src/pull/939

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Move all bluetooth related config files out of etc

This helps with pkgbase by switching to CONFS so they are properly tagged as
config files.

Approved by: will (mentor)
Differential Revision: https://reviews.freebsd.org/D16833