MAINTAINERS: orphan PPP over Ethernet driver

We haven't seen activities from Michal Ostrowski for quite a long time.
The last commit from him is fb64bb5 ("PPPoE: Fix flush/close
races."), which was in 2009. Email to mostrows@earthlink.net also
bounces.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
Link: https://patch.msgid.link/20260401022842.15082-1-dqfext@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: LGA1150

MAINTAINERS

@@ -21075,8 +21075,7 @@ F:	include/uapi/linux/atmppp.h
 F:	net/atm/pppoatm.c
 
 PPP OVER ETHERNET
-M:	Michal Ostrowski <mostrows@earthlink.net>
-S:	Maintained
+S:	Orphan
 F:	drivers/net/ppp/pppoe.c
 F:	drivers/net/ppp/pppox.c