build(deps): update signal-hook requirement from =0.1.8 to =0.3.15

Updates the requirements on [signal-hook](https://github.com/vorner/signal-hook) to permit the latest version.
- [Release notes](https://github.com/vorner/signal-hook/releases)
- [Changelog](https://github.com/vorner/signal-hook/blob/master/CHANGELOG.md)
- [Commits](vorner/signal-hook@v0.1.8...v0.3.15)

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

Signed-off-by: dependabot[bot] <[email protected]>

nsm-test/Cargo.toml

@@ -14,5 +14,5 @@ aws-nitro-enclaves-nsm-api = { path = "../" }
 nsm-lib = { path = "../nsm-lib" }
 nix = "0.20"
 threadpool = "1.7"
-signal-hook = "=0.1.8"
+signal-hook = "0.3"
 vsock = "0.3"

nsm-test/src/bin/nsm-multithread.rs

@@ -140,7 +140,7 @@ fn main() {
     println!("NSM test started.");
 
     let term = Arc::new(atomic::AtomicBool::new(false));
-    signal_hook::flag::register(signal_hook::SIGTERM, Arc::clone(&term))
+    signal_hook::flag::register(signal_hook::consts::SIGTERM, Arc::clone(&term))
         .expect("Failed to register signal hook");
 
     let ctx = nsm_init();