Disable WAL mode for Sqlite pool test

It seems like there are known false positives with thread sanitizer and sqlite.

(There are various references to this in sqlite's wal.c and also possibly
related https://bugzilla.mozilla.org/show_bug.cgi?id=1153409

src/storage/sqlite/Pool.zig

@@ -113,8 +113,6 @@ test "Sqlite: Pool" {
         const conn = try pool.acquire();
         defer pool.release(conn);
 
-        try conn.exec("pragma journal_mode=wal", .{});
-
         // This is not safe and can result in corruption. This is only set
         // because the tests might be run on really slow hardware and we
         // want to avoid having a busy timeout.