fix e2e test: use col instead of val for user_extra

The user_extra table does not have a val column in the e2e schema.

Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>
Signed-off-by: Tanjin Xu <tanjin.xu@slack-corp.com>

Author: tanjinx

go/vt/vtgate/planbuilder/testdata/dml_cases.json

@@ -7433,19 +7433,19 @@
   },
   {
     "comment": "update with IN clause on vindex and limit pushes limit to each shard",
-    "query": "update user_extra set val = 1 where user_id in (1, 2) limit 5",
+    "query": "update user_extra set col = 1 where user_id in (1, 2) limit 5",
     "plan": {
       "Type": "MultiShard",
       "QueryType": "UPDATE",
-      "Original": "update user_extra set val = 1 where user_id in (1, 2) limit 5",
+      "Original": "update user_extra set col = 1 where user_id in (1, 2) limit 5",
       "Instructions": {
         "OperatorType": "Update",
         "Variant": "IN",
         "Keyspace": {
           "Name": "user",
           "Sharded": true
         },
-        "Query": "update user_extra set val = 1 where user_id in ::__vals limit 5",
+        "Query": "update user_extra set col = 1 where user_id in ::__vals limit 5",
         "Table": "user_extra",
         "Values": [
           "(1, 2)"