patch 8.2.4723: the ModeChanged autocmd event is inefficient

Problem:    The ModeChanged autocmd event is inefficient.
Solution:   Avoid allocating memory. (closes #10134)  Rename
            trigger_modechanged() to may_trigger_modechanged().
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 0b88259..7e3cb7e 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -477,7 +477,7 @@
     else
 	exmode_active = EXMODE_NORMAL;
     State = NORMAL;
-    trigger_modechanged();
+    may_trigger_modechanged();
 
     // When using ":global /pat/ visual" and then "Q" we return to continue
     // the :global command.