Require editor restart after changing GUI custom theme or font

The `restart_if_changed` project setting hint wasn't set correctly.

(cherry picked from commit 07244241792e9ebe78f2e7d46a43c7dce74f4a41)

scene/register_scene_types.cpp

@@ -744,9 +744,9 @@ void register_scene_types() {
 
 	bool default_theme_hidpi = GLOBAL_DEF("gui/theme/use_hidpi", false);
 	ProjectSettings::get_singleton()->set_custom_property_info("gui/theme/use_hidpi", PropertyInfo(Variant::BOOL, "gui/theme/use_hidpi", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED));
-	String theme_path = GLOBAL_DEF("gui/theme/custom", "");
+	String theme_path = GLOBAL_DEF_RST("gui/theme/custom", "");
 	ProjectSettings::get_singleton()->set_custom_property_info("gui/theme/custom", PropertyInfo(Variant::STRING, "gui/theme/custom", PROPERTY_HINT_FILE, "*.tres,*.res,*.theme", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED));
-	String font_path = GLOBAL_DEF("gui/theme/custom_font", "");
+	String font_path = GLOBAL_DEF_RST("gui/theme/custom_font", "");
 	ProjectSettings::get_singleton()->set_custom_property_info("gui/theme/custom_font", PropertyInfo(Variant::STRING, "gui/theme/custom_font", PROPERTY_HINT_FILE, "*.tres,*.res,*.font", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED));
 
 	Ref<Font> font;