Tweak the setting hint for the custom editor theme setting

The custom editor theme is only visible after restarting the editor.

(cherry picked from commit 027301fec79d6cd8143f25c95c23c6007279ec23)

editor/editor_settings.cpp

@@ -395,7 +395,7 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	_initial_set("interface/theme/additional_spacing", 0);
 	hints["interface/theme/additional_spacing"] = PropertyInfo(Variant::REAL, "interface/theme/additional_spacing", PROPERTY_HINT_RANGE, "0,5,0.1", PROPERTY_USAGE_DEFAULT);
 	_initial_set("interface/theme/custom_theme", "");
-	hints["interface/theme/custom_theme"] = PropertyInfo(Variant::STRING, "interface/theme/custom_theme", PROPERTY_HINT_GLOBAL_FILE, "*.res,*.tres,*.theme", PROPERTY_USAGE_DEFAULT);
+	hints["interface/theme/custom_theme"] = PropertyInfo(Variant::STRING, "interface/theme/custom_theme", PROPERTY_HINT_GLOBAL_FILE, "*.res,*.tres,*.theme", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED);
 
 	// Scene tabs
 	_initial_set("interface/scene_tabs/show_extension", false);