fix: with -esa and (the experimental) -knc concat were not expanded

lib/l2lExpandArrays.ml

-(** Time-stamp: <modified the 27/02/2024 (at 15:49) by Erwan Jahier> *)
+(** Time-stamp: <modified the 11/03/2024 (at 10:41) by Erwan Jahier> *)
 
 (* Replace structures and arrays by as many variables as necessary.
    Since structures can be nested, it might be a lot of new variables...
@@ -539,11 +539,12 @@ and (expand_val_exp: local_ctx -> acc -> val_exp -> val_exp * acc) =
           | _  -> assert false (* sno *)
         )
       | CALL _
-      | CONCAT | PREDEF_CALL _
+      | PREDEF_CALL _
       | PRE | ARROW | FBY | CURRENT _ | WHEN _ | TUPLE | CONST _
         ->
         let vel,acc = expand_val_exp_list lctx acc vel in
         by_pos_op, acc, vel
+      | CONCAT
       | ARRAY ->
         let vel,acc = expand_val_exp_list lctx acc vel in
         TUPLE, acc,vel