Revert "Adds blinding + blindfolds (#8688)" (#9689)

This reverts commit 7a7ab5e8c1.

Resources/Textures/Shaders/greyscale_fullscreen.swsl

@@ -1,9 +0,0 @@
-uniform sampler2D SCREEN_TEXTURE;
-
-void fragment() {
-    highp vec4 color = zTextureSpec(SCREEN_TEXTURE, UV);
-
-    highp float grey = dot(color.rgb, vec3(0.299, 0.587, 0.114));
-
-    COLOR = vec4(vec3(grey), color.a);
-}