patch 8.2.1720: Vim9: memory leak with heredoc that isn't executed

Problem:    Vim9: memory leak with heredoc that isn't executed. (Dominique
            Pellé)
Solution:   Don't clear the list items. (closes #6991)

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1720,
 /**/
     1719,
 /**/