Mesh: Issue #0004473: Expose openCommand() to translation

Continuing the work to expose the undo/redo functionality to translation. This commit does so for the Mesh Wb.  
Ticket: https://tracker.freecadweb.org/view.php?id=4473

src/Mod/Mesh/Gui/DlgDecimating.cpp

@@ -144,7 +144,7 @@ bool TaskDecimating::accept()
     Gui::Selection().clearSelection();
 
     Gui::WaitCursor wc;
-    Gui::Command::openCommand("Mesh Decimating");
+    Gui::Command::openCommand(QT_TRANSLATE_NOOP("Command", "Mesh Decimating"));
 
     float tolerance = widget->tolerance();
     float reduction = widget->reduction();