Refactor the patch to disable LaterRun

Left over decision from #42630 (comment 3063685).

Basically, do we want to keep disabling the LaterRun module, or drop our patch? I'm not sure the original motivation for disabling it in #41568 (closed) really holds up with our new design document.

For ESR 128, there didn't seem to be much harm in keeping it disabled since there was only one feature that was gated behind it (recommending the user to use the search bar, rather than visiting "duckduckgo.com" directly), and it was only shown if the user re-enabled "Recommend features as you browse", which we disable in Base Browser.

For ESR 140, we will need to review what else might be disabled.

This may be unnecessary maintenance. Plus, there may be future features that we do want to allow users to see the prompts for.