patch 8.2.0753: Vim9: expressions are evaluated in the discovery phase

Problem:    Vim9: expressions are evaluated in the discovery phase.
Solution:   Bail out if an expression is not a constant.  Require a type for
            declared constants.

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    753,
 /**/
     752,
 /**/