patch 8.2.4323: Vim9: nested function name can start with "_"

Problem:    Vim9: nested function name can start with "_".
Solution:   Use same rule for function name for nested functions.
            (closes #9713)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4323,
 /**/
     4322,
 /**/