Clarify the purpose of the default asset library URLs in the editor

`localhost` was removed as it won't work out of the box. It can be added
by the user if they're working on the asset library itself.

This won't affect existing installations due to how the editor settings
are stored, but existing installations will keep working fine.

editor/plugins/asset_library_editor_plugin.cpp

@@ -603,8 +603,7 @@ void EditorAssetLibrary::_notification(int p_what) {
 
 void EditorAssetLibrary::_update_repository_options() {
 	Dictionary default_urls;
-	default_urls["godotengine.org"] = "https://godotengine.org/asset-library/api";
-	default_urls["localhost"] = "http://127.0.0.1/asset-library/api";
+	default_urls["godotengine.org (Official)"] = "https://godotengine.org/asset-library/api";
 	Dictionary available_urls = _EDITOR_DEF("asset_library/available_urls", default_urls, true);
 	repository->clear();
 	Array keys = available_urls.keys();