MAINTAINERS: update STABLE BRANCH info

Drop Chris Wright from STABLE maintainers.  He hasn't done STABLE release
work for quite some time.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Chris Wright <chrisw@sous-sol.org>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>