man pages: Note that votequorum's allow_downscale is unsupported

Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>

man/votequorum.5

@@ -275,6 +275,8 @@ quorum {
 .PP
 Enables allow downscale (AD) feature (default: 0).
 .PP
+THIS FEATURE IS INCOMPLETE AND CURRENTLY UNSUPPORTED.
+.PP
 The general behaviour of votequorum is to never decrease expected votes or quorum.
 .PP
 When AD is enabled, both expected votes and quorum are recalculated when