fix(funnel): TypeError for funnel with display=ActionsLineGraph

This resolves an issue what was introduced by
#5997 where we would fail to
calculate a funnel result if display="ActionsLineGraph" was specified.
The fix was simply to wrap a string in `sql.SQL`.

Resolves #6530

posthog/queries/funnel.py

@@ -192,7 +192,7 @@ def _build_trends_query(self, filter: Filter) -> sql.SQL:
         ).format(
             interval=sql.Literal(filter.interval),
             particular_steps=sql.SQL(",\n").join(particular_steps),
-            steps_query=self._build_query(within_time="'1 day'"),
+            steps_query=sql.SQL(self._build_query(within_time="'1 day'")),
             interval_field=sql.SQL("step_0")
             if filter.interval != "week"
             else sql.SQL("(\"step_0\" + interval '1 day') AT TIME ZONE 'UTC'"),