UI: Add missing icons for Undo/Redo in Edit menu

These are pretty universal and could be used as icon-only buttons,
so it's good to use them to create a visual connection.

scripts/startup/bl_ui/space_text.py

@@ -391,8 +391,8 @@ class TEXT_MT_edit(Menu):
     def draw(self, _context):
         layout = self.layout
 
-        layout.operator("ed.undo")
-        layout.operator("ed.redo")
+        layout.operator("ed.undo", icon='LOOP_BACK')
+        layout.operator("ed.redo", icon='LOOP_FORWARDS')
 
         layout.separator()
 

scripts/startup/bl_ui/space_topbar.py

@@ -495,8 +495,8 @@ class TOPBAR_MT_edit(Menu):
 
         show_developer = context.preferences.view.show_developer_ui
 
-        layout.operator("ed.undo")
-        layout.operator("ed.redo")
+        layout.operator("ed.undo", icon='LOOP_BACK')
+        layout.operator("ed.redo", icon='LOOP_FORWARDS')
         layout.menu("TOPBAR_MT_undo_history")
 
         layout.separator()