userns: Enable building of pf_key sockets when user namespace support is enabled.

Enable building of pf_key sockets and user namespace support at the
same time.  This combination builds successfully so there is no reason
to forbid it.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

init/Kconfig

@@ -944,7 +944,6 @@ config UIDGID_CONVERTED
 	# Networking
 	depends on NET_9P = n
 	depends on AF_RXRPC = n
-	depends on NET_KEY = n
 	depends on DNS_RESOLVER = n
 
 	# Filesystems