Remove materialized option from Basic.fetch_jobs/3

The `MATERIALIZED` clause for CTEs didn't make a meaningful difference
in job fetching accuracy. In some situations it caused a performance
regression (which is why it was removed from Pro's Smart engine a while
ago).

lib/oban/engines/basic.ex

@@ -104,7 +104,7 @@ defmodule Oban.Engines.Basic do
     # of the CTE, e.g. "public"."subset".
     query =
       Job
-      |> with_cte("subset", as: ^subset_query, materialized: true)
+      |> with_cte("subset", as: ^subset_query)
       |> join(:inner, [j], x in fragment(~s("subset")), on: true)
       |> where([j, x], j.id == x.id)
       |> where([j, _], j.attempt < j.max_attempts)