doc: use built-in parse-long in tutorial.

[olepbr]

Hi!

Teeny-tiny PR here.

As noted in 74989931bbdd19d6dcf65e8a9261383d7c57bc21, Clojure 1.11 gave us parse-long, which handles nil the way we'd like it to, so writing a wrapper for Long/parseLong is no longer necessary. so we can use that instead of Long/parseLong.

This PR thus amends that section of the tutorial.

Cheers for a great library :–)

[olepbr]

Actually, it does not, as it throws IllegalArgumentException when it's passed nil, my bad! It's still maybe preferable to use it in the wrapper instead of parseLong, though?

[olepbr]

It's still maybe preferable to use it in the wrapper instead of parseLong, though?

I updated the PR to do this instead. parse-long-nil isn't a great name though. Naming things, etc.

[aphyr]

okay