patch 8.2.1870: Vim9: no need to keep all script variables

Problem:    Vim9: no need to keep all script variables.
Solution:   Only keep script variables when a function was defined that could
            use them.  Fix freeing static string on exit.
diff --git a/src/version.c b/src/version.c
index a0bc135..835de6c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1870,
+/**/
     1869,
 /**/
     1868,