Restore accidentaly removed comment line.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation

etc/autofs/special_media

@@ -21,6 +21,7 @@ print_available() {
 			_label="${_fstype_and_label#* }"
 			# Replace plus signs and slashes with minuses;
 			# leading plus signs have special meaning in maps,
+			# and multi-component keys are just not supported.
 			_label="$(echo ${_label} | sed 's,[+/],-,g')"
 			echo "${_label}"
 			continue