MAINTAINERS: Add Vladimir as a reviewer for bitmaps

I already try to make sure all bitmaps patches have been reviewed by both
Red Hat and Virtuozzo anyway, so this formalizes the arrangement.

Fam meanwhile is no longer as active, so I am removing him as a co-maintainer
simply to reflect the current practice.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20191005194448.16629-2-jsnow@redhat.com

MAINTAINERS

@@ -1816,8 +1816,8 @@ F: qapi/transaction.json
 T: git https://repo.or.cz/qemu/armbru.git block-next
 
 Dirty Bitmaps
-M: Fam Zheng <fam@euphon.net>
 M: John Snow <jsnow@redhat.com>
+R: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
 L: qemu-block@nongnu.org
 S: Supported
 F: util/hbitmap.c
@@ -1826,7 +1826,6 @@ F: include/qemu/hbitmap.h
 F: include/block/dirty-bitmap.h
 F: tests/test-hbitmap.c
 F: docs/interop/bitmaps.rst
-T: git https://github.com/famz/qemu.git bitmaps
 T: git https://github.com/jnsnow/qemu.git bitmaps
 
 Character device backends