MAINTAINERS: Drop RDMA files from Hyper-V section

MAINTAINERS: Drop RDMA files from Hyper-V section

MAINTAINERS entries are organized by subsystem ownership, and the RDMA
files belong under drivers/infiniband. Remove the overly broad mana_ib
entries from the Hyper-V section, and instead add the Hyper-V mailing list
to CC on mana_ib patches.

This makes get_maintainer.pl behave more sensibly when running it on
mana_ib patches.

Fixes: 428ca2d4c6aa ("MAINTAINERS: Add Long Li as a Hyper-V maintainer")
Link: https://patch.msgid.link/20260128-get-maintainers-fix-v1-1-fc5e58ce9f02@nvidia.com
Reviewed-by: Long Li <longli@microsoft.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>