README style/typo fixes: "web server" and possessive "Rails'"

[aried3r]

I think this "f" isn't meant to be there.

I've replaced "webserver" with "web server" everywhere as it seems that's also what Rails and puma use and the README itself also uses "web server" half of the time.

There's an unfinished or unintentional beginning of a markdown link here ([GoodJob.preserve_job_records), but I'm not sure where this should point, if anywhere at all.

good_job/README.md

Line 180 in 9517669

`good_job cleanup_preserved_jobs` deletes preserved job records. See [`GoodJob.preserve_job_records` for when this command is useful.

[bensheldon]

@aried3r thank you! 🙌