Fix typo: defualt -> default

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

man/corosync.conf.5

@@ -537,7 +537,7 @@ The default is off.
 blackbox
 This specifies that blackbox functionality should be enabled.
 
-The defualt is on.
+The default is on.
 
 .PP
 The following options are valid both for top level logging directive