journald-server: drop another invalid assert()

config_parse_forward_to_socket() is not used for parsing unit files
either.

Follow-up-for: f31cff849d

src/journal/journald-server.c

@@ -3057,7 +3057,6 @@ int config_parse_forward_to_socket(
         SocketAddress* addr = ASSERT_PTR(data);
         int r;
 
-        assert(unit);
         assert(filename);
         assert(rvalue);