patch 8.2.2306: Vim9: when using function reference type is not checked

Problem:    Vim9: when using function reference type is not checked.
Solution:   When using a function reference lookup the type and check the
            argument types. (issue #7629)

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2306,
 /**/
     2305,
 /**/