Drop unused winbox_frame backward-compat alias

Nothing in the tree uses it; it was added during the rename out of an
abundance of caution but there are no callers.

lib/galaxy/selenium/navigates_galaxy.py

@@ -2335,9 +2335,6 @@ class NavigatesGalaxy(HasDriverProxy[WaitType]):
         finally:
             self.switch_to_default_content()
 
-    # backward compat alias
-    winbox_frame = scratchbook_frame
-
     def window_manager_get_titles(self) -> list:
         """Return list of window titles from all open scratchbook windows."""
         elements = self.components.window_manager.title.all()