wxGUI: do not crash on localized GUIs (OSGeo#2488)

PR OSGeo#2469 (908c5e2) introduced
a code that uses English UI strings to identify UI elements.
In the case of a translated UI it fails to get element and then
proceeds to manipulate with not existing element leading to
an assert in C++ wx code.

gui/wxpython/lmgr/workspace.py

@@ -505,10 +505,10 @@ def CreateRecentFilesMenu(self, menu=None):
         """
         if menu:
             file_menu = menu.GetMenu(
-                menuIndex=menu.FindMenu(title="File"),
+                menuIndex=menu.FindMenu(title=_("File")),
             )
             workspace_item = file_menu.FindItem(
-                id=file_menu.FindItem(itemString="Workspace"),
+                id=file_menu.FindItem(itemString=_("Workspace")),
             )[0]
             self._recent_files = RecentFilesMenu(
                 app_name="main",