transmission-remote-gtk: fix TLS support

Since https://github.com/NixOS/nixpkgs/pull/254042, transmission-remote-gtk shows an error that TLS support is not enabled when connecting over TLS. This fixes that for me.

pkgs/applications/networking/p2p/transmission-remote-gtk/default.nix

···
     libmrss
     libproxy
     libsoup_3
-  ];
+  ] ++ libsoup_3.propagatedUserEnvPackages;
 
   doCheck = false; # Requires network access