Improve docs for UdpSocket::set_nonblocking.

[frewsxcv]

Closes#44050.

[rust-highfive]

r? @sfackler

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[frewsxcv]

@sfackler one more here when you have a moment

[sfackler]

Stray /

[sfackler]

Also send_to/recv_from

[sfackler]

Would it be simpler to not connect and use send_to/recv_from instead?

[sfackler]

No need for this continue.

[frewsxcv]

@sfackler thanks for the review! comments addressed in the latest commit

[kennytm]

CI is failing. Note that .recv_from returns a Result<(usize, SocketAddr)>, not Result<usize>.

[01:04:03] ---- net/udp.rs - net::udp::UdpSocket::set_nonblocking (line 742) stdout ----
[01:04:03] error[E0277]: the trait bound `std::ops::RangeTo<(usize, std::net::SocketAddr)>: std::slice::SliceIndex<[u8]>` is not satisfied
[01:04:03] --> net/udp.rs:23:26
[01:04:03] |
[01:04:03] 23 | println!("bytes: {:?}", &buf[..num_bytes_read]);
[01:04:03] | ^^^^^^^^^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
[01:04:03] |
[01:04:03] = help: the trait `std::slice::SliceIndex<[u8]>` is not implemented for `std::ops::RangeTo<(usize, std::net::SocketAddr)>`
[01:04:03] = note: required because of the requirements on the impl of `std::ops::Index<std::ops::RangeTo<(usize, std::net::SocketAddr)>>` for `[u8]`
[01:04:03] [01:04:03] thread 'rustc' panicked at 'couldn't compile the test', /checkout/src/librustdoc/test.rs:287:12
[01:04:03] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[01:04:03] [01:04:03] [01:04:03] failures:
[01:04:03] net/udp.rs - net::udp::UdpSocket::set_nonblocking (line 742)
[01:04:03] [01:04:03] test result: FAILED. 876 passed; 1 failed; 10 ignored; 0 measured; 0 filtered out

[frewsxcv]

ci passes now

[sfackler]

@bors r+ rollup

[bors]

📌 Commit 04f27f0 has been approved by sfackler