Fix #124753: Tag preferences dirty when editing operator property

When operator property is tweaked in preferences > keymap > "any operator",
preferences are not tagged dirty, which prevents writing the userpref
file at `WM_exit_ex` when auto-save is enabled.

Pull Request: https://projects.blender.org/blender/blender/pulls/128516

source/blender/editors/interface/templates/interface_templates.cc

@@ -6827,6 +6827,7 @@ static void keymap_item_modified(bContext * /*C*/, void *kmi_p, void * /*unused*
 {
   wmKeyMapItem *kmi = (wmKeyMapItem *)kmi_p;
   WM_keyconfig_update_tag(nullptr, kmi);
+  U.runtime.is_dirty = true;
 }
 
 static void template_keymap_item_properties(uiLayout *layout, const char *title, PointerRNA *ptr)