patch 8.2.1685: Vim9: cannot declare a constant value

Problem:    Vim9: cannot declare a constant value.
Solution:   Introduce ":const!".
diff --git a/src/version.c b/src/version.c
index 67ccfb6..f958df9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1685,
+/**/
     1684,
 /**/
     1683,