patch 8.2.3886: can define autocmd for every event by using "au!"

Problem:    Can define autocmd for every event by using "au!".
Solution:   Check if a command is present also for "au!".

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3886,
 /**/
     3885,
 /**/