main: add missing comma after AlwaysPairable

main: add missing comma after AlwaysPairable

Commit 1880b2990866 ("core: Add AlwaysPairable to main.conf") added a new
key to supported_options but didn't add a comma. This leads to the
following error message on startup if the key 'PairableTimeout' is pesent:

Unknown key PairableTimeout for group General in /etc/bluetooth/main.conf

This probably also leads to ignoring the setting.

Fixes: 1880b2990866 ("core: Add AlwaysPairable to main.conf")

Change-Id: I193e6da4956605a932f08d2f4ec3000e23fc2bb5
Signed-off-by: DoHyun Pyun <dh79.pyun@samsung.com>