gnomeExtensions: Fix the package names

I did not realize the attribute names are derived from the Nix package names
so I accidentally, renamed them in https://github.com/NixOS/nixpkgs/pull/124295.

pkgs/desktops/gnome/extensions/buildGnomeExtension.nix

@@ -47,8 +47,11 @@ let
       license = lib.licenses.gpl2Plus; # https://wiki.gnome.org/Projects/GnomeShell/Extensions/Review#Licensing
       maintainers = with lib.maintainers; [ piegames ];
     };
-    # Store the extension's UUID, because we might need it at some places
-    passthru.extensionUuid = uuid;
+    passthru = {
+      extensionPortalSlug = pname;
+      # Store the extension's UUID, because we might need it at some places
+      extensionUuid = uuid;
+    };
   };
 in
   lib.makeOverridable buildGnomeExtension

pkgs/desktops/gnome/extensions/default.nix

@@ -48,7 +48,7 @@ let
     ))
     # Map all extensions to their pname, with potential overwrites
     (map (extension:
-      lib.nameValuePair (extensionRenames.${extension.extensionUuid} or extension.pname) extension
+      lib.nameValuePair (extensionRenames.${extension.extensionUuid} or extension.extensionPortalSlug) extension
     ))
     builtins.listToAttrs
   ];