patch 8.2.2926: Vim9: no good error for using :legacy in a :def function

Problem:    Vim9: no good error for using :legacy in a :def function.
Solution:   Give an explicit error where :legacy is not working.
            (closes #8309)
diff --git a/src/version.c b/src/version.c
index 188bb1a..6761b72 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2926,
+/**/
     2925,
 /**/
     2924,