MAINTAINERS: remove RTDS specific entry

Remove the RTDS scheduler specific entry in MAINTAINERS.

The effective changes will be:

- Meng will no longer be a maintainer. His last Ack on a RTDS patch
  was given in 2019, since then I can't remember having seen any
  reaction on a RTDS patch.

- I'll be made a maintainer of this scheduler. Dario has indicated
  that he doesn't have lots of cycles for doing reviews, so he would
  be grateful for not being effectively the only maintainer of the
  RTDS scheduler.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

MAINTAINERS

@@ -515,12 +515,6 @@ S:	Supported
 F:	config/riscv64.mk
 F:	xen/arch/riscv/
 
-RTDS SCHEDULER
-M:	Dario Faggioli <dfaggioli@suse.com>
-M:	Meng Xu <mengxu@cis.upenn.edu>
-S:	Supported
-F:	xen/common/sched/rt.c
-
 SCHEDULING
 M:	Dario Faggioli <dfaggioli@suse.com>
 M:	Juergen Gross <jgross@suse.com>