MAINTAINERS: Remove an invalid path of RZ Platforms

Since the folder soc/renesas/rzt2m has been moved into soc/renesas/rz
to unify with other RZ devices, so the path soc/renesas/rzt2m must be
removed to pass pipeline.

Signed-off-by: Nhut Nguyen <nhut.nguyen.kc@renesas.com>
Signed-off-by: Binh Nguyen <binh.nguyen.xw@renesas.com>