gui.txt: Update Vim 9.0.0946

Author: tsuyoshicho

en/gui.txt

@@ -1,4 +1,4 @@
-*gui.txt*       For Vim version 9.0.  Last change: 2022 Apr 03
+*gui.txt*       For Vim version 9.0.  Last change: 2022 Nov 17
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -889,6 +889,11 @@ s	The menu was defined with "<silent>" to avoid showing what it is
 Note that hitting <Tab> while entering a menu name after a menu command may
 be used to complete the name of the menu item.
 
+It is not allowed to change menus while listing them.  *E1310*
+This doesn't normally happen, only when, for example, you would have a timer
+callback define a menu and the user lists menus in a way it shows
+|more-prompt|.
+
 
 5.4 Executing Menus					*execute-menus*