nixos/gnome: drop shared-mime-info

It is already installed by xdg.mime.enable.

Let’s also enable that option explicitly to prevent users from accidentally
disabling it since GNOME will be severely broken without it.

nixos/modules/services/x11/desktop-managers/gnome.nix

@@ -367,6 +367,9 @@ in
       services.upower.enable = config.powerManagement.enable;
       services.xserver.libinput.enable = mkDefault true; # for controlling touchpad settings via gnome control center
 
+      # Explicitly enabled since GNOME will be severely broken without it.
+      xdg.mime.enable = true;
+
       xdg.portal.enable = true;
       xdg.portal.extraPortals = [
         pkgs.xdg-desktop-portal-gnome
@@ -469,7 +472,6 @@ in
         pkgs.gnome-menus
         pkgs.gtk3.out # for gtk-launch
         pkgs.hicolor-icon-theme
-        pkgs.shared-mime-info # for update-mime-database
         pkgs.xdg-user-dirs # Update user dirs as described in http://freedesktop.org/wiki/Software/xdg-user-dirs/
       ];
     })