MAINTAINERS: wifi: rt2x00: drop Helmut Schaa

Helmut hasn't been responding to rt2x00 related emails since 2016,
remove him from rt2x00 mainterner list.
Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231019202651.518136-1-stf_xl@wp.pl

MAINTAINERS

@@ -17932,7 +17932,6 @@ F:	arch/mips/boot/dts/ralink/mt7621*
 
 RALINK RT2X00 WIRELESS LAN DRIVER
 M:	Stanislaw Gruszka <stf_xl@wp.pl>
-M:	Helmut Schaa <helmut.schaa@googlemail.com>
 L:	linux-wireless@vger.kernel.org
 S:	Maintained
 F:	drivers/net/wireless/ralink/rt2x00/