man: votequorum.5: use proper single quotes

Backtick and apostrophe are formatted as directional quotes by plain
groff, but they behave literally in the body of a man page.

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

man/votequorum.5

@@ -266,7 +266,7 @@ be inquorate. This behaviour can be changed by also specifying
 .PP
 .B auto_tie_breaker_node: lowest|highest|<list of node IDs>
 .PP
-\'lowest' is the default, 'highest' is similar in that if the current set of
+\(oqlowest\(cq is the default, \(oqhighest\(cq is similar in that if the current set of
 nodes contains the highest nodeid then it will remain quorate. Alternatively
 it is possible to specify a particular node ID or list of node IDs that will 
 be required to maintain quorum. If a (space-separated) list is given, the