Update signal-hook requirement from 0.3 to 0.4 (#363)

Updates the requirements on [signal-hook](https://github.com/vorner/signal-hook) to permit the latest version.
- [Changelog](https://github.com/vorner/signal-hook/blob/master/CHANGELOG.md)
- [Commits](vorner/signal-hook@v0.3.0...v0.4.1)

---
updated-dependencies:
- dependency-name: signal-hook
  dependency-version: 0.4.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Taiki Endo <te316e89@gmail.com>

Author: dependabot[bot]

Cargo.toml

@@ -43,7 +43,7 @@ hyper = { version = "1.0", default-features = false, features = ["client", "http
 macro_rules_attribute = "0.2.0"
 native-tls = "0.2"
 scraper = "0.25"
-signal-hook = "0.3"
+signal-hook = "0.4"
 smol-hyper = "0.1.0"
 smol-macros = "0.1.0"
 surf = { version = "2", default-features = false, features = ["h1-client"] }

examples/unix-signal.rs

@@ -8,15 +8,15 @@
 
 #[cfg(unix)]
 fn main() -> std::io::Result<()> {
-    use std::os::unix::{io::AsRawFd, net::UnixStream};
+    use std::os::unix::net::UnixStream;
 
     use smol::{prelude::*, Async};
 
     smol::block_on(async {
         // Create a Unix stream that receives a byte on each signal occurrence.
         let (a, mut b) = Async::<UnixStream>::pair()?;
         // Async isn't IntoRawFd, but it is AsRawFd, so let's pass the raw fd directly.
-        signal_hook::low_level::pipe::register_raw(signal_hook::consts::SIGINT, a.as_raw_fd())?;
+        signal_hook::low_level::pipe::register_raw(signal_hook::consts::SIGINT, a.try_into()?)?;
         println!("Waiting for Ctrl-C...");
 
         // Receive a byte that indicates the Ctrl-C signal occurred.