remove the now-upstream console background patch

modules/gnome-console-tweaks/background.patch

@@ -1,9 +0,0 @@
---- a/src/kgx-terminal.c
-+++ b/src/kgx-terminal.c
-@@ -159,5 +159,5 @@ update_terminal_colors (KgxTerminal *self)
-     default:
-       fg = (GdkRGBA) { 1.0, 1.0, 1.0, 1.0};
--      bg = (GdkRGBA) { 0.05, 0.05, 0.05, 0.96 };
-+      bg = (GdkRGBA) { 0.12, 0.12, 0.12, 1.0 };
-       break;
-   }

modules/gnome-console-tweaks/default.nix

@@ -2,8 +2,12 @@
   nixpkgs.overlays = [
     (self: super: {
       gnome-console = super.gnome-console.overrideAttrs (prev: {
-        patches = prev.patches ++ [
-          ./background.patch
+        patches =
+          (
+            if (builtins.elem "patches" (builtins.attrNames prev))
+            then prev.patches
+            else [ ]
+          ) ++ [
             ./no-close-tab-prompt.patch
             ./tango.patch
           ];