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.

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1870,
 /**/
     1869,
 /**/