man: fix section of virt-sanlock-cleanup

Reported at build time by lintian:
manpage-section-mismatch usr/share/man/man8/virt-sanlock-cleanup.8.gz:3 8 != 1

And indeed the rst file says 1 while the makefile say 8:
 if WITH_SANLOCK
   manpages8_rst += manpages/virt-sanlock-cleanup.rst
 else ! WITH_SANLOCK

8 "System administration commands and daemons" seems to match, so fix
the rst file to match.
Signed-off-by: NChristian Ehrhardt <christian.ehrhardt@canonical.com>
Reviewed-by: NDaniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

docs/manpages/virt-sanlock-cleanup.rst

@@ -6,7 +6,7 @@ virt-sanlock-cleanup
 remove stale sanlock resource lease files
 -----------------------------------------
 
-:Manual section: 1
+:Manual section: 8
 :Manual group: Virtualization Support
 
 .. contents::