MAINTAINERS: Drop Aneesh as 9pfs maintainer

Aneesh has been working on other topics for some time now. Let's reflect
that in the MAINTAINERS file, so that people stop Cc'ing him.

Signed-off-by: Greg Kurz <groug@kaod.org>
Acked-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>