MAINTAINERS: remove reference to bogus vsock file

The file drivers/vhost/vsock.h never existed.  Remove the bogus
MAINTAINERS reference.

Fixes: 433fc58e6bf2c8bd97e57153ed28e64fd78207b8 ("VSOCK: Introduce vhost_vsock.ko")
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

MAINTAINERS

@@ -15542,7 +15542,6 @@ F:	net/vmw_vsock/virtio_transport_common.c
 F:	net/vmw_vsock/virtio_transport.c
 F:	drivers/net/vsockmon.c
 F:	drivers/vhost/vsock.c
-F:	drivers/vhost/vsock.h
 F:	tools/testing/vsock/
 
 VIRTIO CONSOLE DRIVER