### Godot version

v4.2.dev3.official [013e8e3af]

### System information

Windows 11, Core i5-12400F, RX 6600

### Issue description

TileSet->Setup->Separation maybe should have "px" like rest?
![Screenshot 2023-08-21 162202](https://github.com/godotengine/godot/assets/962340/3c6b9a97-7520-4610-8153-7882cc9c303f)
I know this is pixels from testing it.

TileSet->Select is this Animation Separation "px" too? idk
![Screenshot 2023-08-21 162131](https://github.com/godotengine/godot/assets/962340/fcb580e3-9ff7-41d8-92d3-e585841d3803)
I tried setting up animation separation and got a not enough room error, so maybe not "px". idk


Thanks.


### Steps to reproduce

- open TileSet->Setup->Separation, note some have "px" and one doesn't
- open TileSet->Select, is this separation "px" too?


### Minimal reproduction project

n/a
for (int x = 0; x < grid_size.x; x++) {
				
				Vector2i coords = Vector2i(x, y);
				if (tile_set_atlas_source->get_tile_at_coords(coords) == TileSetSource::INVALID_ATLAS_COORDS) {
					
					Rect2i region = Rect2i(margins + (coords * (texture_region_size + separation)), texture_region_size);
					bool is_opaque = false;
					for (int region_x = region.get_position().x; region_x < region.get_end().x; region_x++) {
						for (int region_y = region.get_position().y; region_y < region.get_end().y; region_y++) {
							if (texture->is_pixel_opaque(region_x, region_y)) {
								is_opaque = true;
								break;
							}
						}
						if (is_opaque) {
							break;
						}
					}
					
					if (is_opaque) {
						undo_redo->add_do_method(tile_set_atlas_source, "create_tile", coords);
						undo_redo->add_undo_method(tile_set_atlas_source, "remove_tile", coords);
					}
				}
			}
		}
		undo_redo->commit_action();
	}
}
void TileSetAtlasSourceEditor::_auto_remove_tiles() {