python.nbxmpp: Fix dependency specs

These deps are actually needed at runtime, not just for the test suite.

This presumably hasn't been noticed until now because gajim, the only
consumer of nbxmpp, already depends on all three of these packages
anyway.

However, gajim only depends on libsoup transitively through gupnp-igd, and
thus fails to build if the dependency on that is disabled by passing
enableUPnP = false.

pkgs/development/python-modules/nbxmpp/default.nix

@@ -15,8 +15,7 @@ in buildPythonPackage {
   };
 
   buildInputs = [ precis-i18n ];
-  checkInputs = [ gobject-introspection libsoup pygobject3 ];
-  propagatedBuildInputs = [ idna pyopenssl ];
+  propagatedBuildInputs = [ gobject-introspection idna libsoup pygobject3 pyopenssl ];
 
   meta = with lib; {
     homepage = "https://dev.gajim.org/gajim/python-nbxmpp";