patch 8.2.0721: Vim9: leaking memory when skipping

Problem:    Vim9: leaking memory when skipping.
Solution:   Disable skipping in generate_ppconst().
diff --git a/src/version.c b/src/version.c
index 456516f..f51f51d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    721,
+/**/
     720,
 /**/
     719,