Show MetalFX options in the Scaling 3D Mode enum on all platforms

Previously, the MetalFX scaling modes were only displayed in the
`macos` and `ios` feature tag overrides if the editor had Metal support
enabled. However, this is only available on the macOS editor, which caused
two issues:

- You couldn't set the 3D scaling mode to MetalFX for `macos` or `ios`
  if you were using the editor on another platform.
- If you opened a project that was last edited on macOS with MetalFX scaling
  modes set for these overrides, it would show an unknown value or revert
  to the default when saving to the project (as the enum value didn't exist
  anymore on your end).

servers/rendering_server.cpp

@@ -3670,10 +3670,9 @@ void RenderingServer::init() {
 		{
 			Vector<String> mode_hints_arr = { "Bilinear (Fastest)", "FSR 1.0 (Fast)", "FSR 2.2 (Slow)" };
 			mode_hints = String(",").join(mode_hints_arr);
-#ifdef METAL_ENABLED
+
 			mode_hints_arr.push_back("MetalFX (Spatial)");
 			mode_hints_arr.push_back("MetalFX (Temporal)");
-#endif
 			mode_hints_metal = String(",").join(mode_hints_arr);
 		}