I18n: fix translation of undo history

The Undo History menu displays each undo step's name. These are either
operators or property names. Operators are translated upon display,
and they use the operator name. Currently, many of them are not
translated because they do not use the proper translation
context.

This commit changes the translation context to
BLT_I18NCONTEXT_OPERATOR_DEFAULT ("Operator").

Pull Request: https://projects.blender.org/blender/blender/pulls/108872

source/blender/editors/space_topbar/space_topbar.c

@@ -256,7 +256,7 @@ static void undo_history_draw_menu(const bContext *C, Menu *menu)
     uiLayout *row = uiLayoutRow(column, false);
     uiLayoutSetEnabled(row, !is_active);
     uiItemIntO(row,
-               IFACE_(us->name),
+               CTX_IFACE_(BLT_I18NCONTEXT_OPERATOR_DEFAULT, us->name),
                is_active ? ICON_LAYER_ACTIVE : ICON_NONE,
                "ED_OT_undo_history",
                "item",