MAINTAINERS: Remove bouncing T7XX reviewer

This reviewer's email no longer works. Remove it from MAINTAINERS.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Chandrashekar Devegowda <chandrashekar.devegowda@intel.com>
Cc: Liu Haijun <haijun.liu@mediatek.com>
Cc: Ricardo Martinez <ricardo.martinez@linux.intel.com>
Link: https://patch.msgid.link/20250808173925.FECE3782@davehans-spike.ostc.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: hansendc

MAINTAINERS

@@ -15672,7 +15672,6 @@ MEDIATEK T7XX 5G WWAN MODEM DRIVER
 M:	Chandrashekar Devegowda <chandrashekar.devegowda@intel.com>
 R:	Chiranjeevi Rapolu <chiranjeevi.rapolu@linux.intel.com>
 R:	Liu Haijun <haijun.liu@mediatek.com>
-R:	M Chetan Kumar <m.chetan.kumar@linux.intel.com>
 R:	Ricardo Martinez <ricardo.martinez@linux.intel.com>
 L:	netdev@vger.kernel.org
 S:	Supported