Remove Horizon draw-surface patch

Does not seem to be necessary any more.

overlays/default.nix

@@ -2,6 +2,5 @@
 {
     imports = [
         ./burp.nix
-        ./horizon-eda.nix
     ];
 }

overlays/horizon-eda.nix

@@ -1,13 +0,0 @@
-{ config, ... }:
-{
-    nixpkgs.overlays = [
-        (self: super: {
-            horizon-eda = (super.horizon-eda.overrideAttrs (old: {
-                # Add an environment variable to fix redraw issues on Intel Graphics
-                patches = [
-                    ./horizon_software_draw_surface.patch
-                ];
-            }));
-        })
-    ];
-}

overlays/horizon_software_draw_surface.patch

@@ -1,10 +0,0 @@
-diff --git a/org.horizon_eda.HorizonEDA.desktop b/org.horizon_eda.HorizonEDA.desktop
-index 7551df54..d8df7800 100644
---- a/org.horizon_eda.HorizonEDA.desktop
-+++ b/org.horizon_eda.HorizonEDA.desktop
-@@ -5,4 +5,4 @@ Categories=Development;Engineering;Electronics;
- Type=Application
- Terminal=false
- Icon=org.horizon_eda.HorizonEDA
--Exec=horizon-eda %U
-+Exec=env GDK_GL=software-draw-surface horizon-eda %U