patch 8.2.3913: help for expressions does not mention Vim9 syntax

Problem:    Help for expressions does not mention Vim9 syntax.
Solution:   Add the rules for Vim9 to the expression help.  Rename functions
            to match the help.
diff --git a/src/version.c b/src/version.c
index 06a0a33..658d9be 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3913,
+/**/
     3912,
 /**/
     3911,