Fix invalid values call for update statement

The previous statement generated a `BindParameter` that could not be serialized to JSON. This change switches to a Tuple that gets serialized successfully.
It throwed a `TypeError` when trying to serialize

src/crate/client/sqlalchemy/tests/dict_test.py

@@ -98,9 +98,7 @@ def test_update_with_dict_column(self):
         mytable = self.mytable
         stmt = mytable.update().\
             where(mytable.c.name == 'Arthur Dent').\
-            values({
-                "data['x']": "Trillian"
-            })
+            values({mytable.c.data['x']: "Trillian"})
         self.assertSQL(
             "UPDATE mytable SET data['x'] = ? WHERE mytable.name = ?",
             stmt