Fix Rust blog link in README

[Bvegas882]

Description

Replace the outdated Rust blog link in README with the stable docs homepage.

• The current URL https://blog.rust-lang.org/2020/02/27/Rust-1.63.0.html has a year path that doesn’t correspond to Rust 1.63, which risks confusion or link rot.
• The crate explicitly targets Rust 1.63 (see Cargo.toml), so linking to https://doc.rust-lang.org/ provides a stable, authoritative target without implying a specific release post date.
• No code or CI changes; documentation only.

[apoelstra]

Can you change the URL to https://releases.rs/docs/1.63.0/ instead? This is still precise, but doesn't have a date that is easy to get wrong.

[Bvegas882]

Hi @apoelstra, done as request, pls check, thanks!

[tcharding]

CI fail is unrelated, obviously.

[tcharding]

I confirmed the link works. Thanks.

[apoelstra]

In my local CI I have changed the Ordering::Relaxed to Ordering::SeqCst in src/lib.rs test_random_32_bytes which seems to have fixed this test's flakiness. But it's hard to say because it usually passes anyway, so I'd to give it a bit more time before PR'ing it.

[apoelstra]

ACK 1fcbb4f; successfully ran local tests

[apoelstra]

ACK c247ed7; successfully ran local tests