📌 fix(ci): pin nightly toolchain

[cratelyn]

this ci action fails due to tkaitchuck/aHash#200.

[cratelyn]

the rustdoc build script uses +nightly. we'll need to sort out how to thread that through from the github action for future nightly breakages like this.

[conorsch]

Nice, thanks for jumping on this, I hadn't started debugging the nightly failure.

[cratelyn]

Nice, thanks for jumping on this, I hadn't started debugging the nightly failure.

credit to tracking down the upstream issue goes to @erwanor 🥇

[conorsch]

the rustdoc build script uses +nightly

I patched the rust-docs build script to use nightly-2024-02-01 as a temporary workaround. Builds locally for me again, so CI should pass, too.