man: corosync-cfgtool.8: use proper single quotes

Apostrophe as the first character of the input line indicates a
request, so groff complained: macro 'onwire'' not defined.

Signed-off-by: Ferenc Wágner <wferi@debian.org>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>

man/corosync-cfgtool.8

@@ -88,7 +88,7 @@ nodeid: 2 reachable   onwire (min/max/cur): 0, 1, 1
 .P
 Only reachable nodes are displayed so "reachable" should always be there.
 .br
-'onwire' versions are the knet on-wire versions that are supported/in use (where appropriate).
+\(oqonwire\(cq versions are the knet on-wire versions that are supported/in use (where appropriate).
 .br
 IP addresses are the local and remote IP addresses (for UDP[U] only the local IP address is shown)
 .br