patch 8.2.1931: Vim9: arguments of extend() not checked at compile time

Problem:    Vim9: arguments of extend() not checked at compile time.
Solution:   Add argument type checking for extend().

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1931,
 /**/
     1930,
 /**/