autofs: Remove stale comment

devd action for automount -c was never commented.

Sponsored by:	Beckhoff Automation GmbH & Co. KG
Differential Revision:	https://reviews.freebsd.org/D42493
Reviewed by:	rew

usr.sbin/autofs/auto_master

@@ -2,7 +2,5 @@
 # Automounter master map, see auto_master(5) for details.
 #
 /net		-hosts		-nobrowse,nosuid,intr
-# When using the -media special map, make sure to edit devd.conf(5)
-# to move the call to "automount -c" out of the comments section.
 #/media		-media		-nosuid,noatime,autoro
 #/-		-noauto