MAINTAINERS: Remove net/core/flow.c

net/core/flow.c does not exist anymore, so remove it
from the IPSEC NETWORKING section of the MAINTAINERS
file.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

MAINTAINERS

@@ -10130,7 +10130,6 @@ L:	netdev@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec.git
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next.git
 S:	Maintained
-F:	net/core/flow.c
 F:	net/xfrm/
 F:	net/key/
 F:	net/ipv4/xfrm*