build(deps): update nix requirement

Updates the requirements on [nix](https://github.com/nix-rust/nix) to permit the latest version.

Updates `nix` to 0.30.1
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](nix-rust/nix@v0.29.0...v0.30.1)

---
updated-dependencies:
- dependency-name: nix
  dependency-version: 0.30.1
  dependency-type: direct:production
  dependency-group: vhost
...

Signed-off-by: dependabot[bot] <[email protected]>
[SG] adapted the memfd_create call to comply with the new nix v0.30
     interface
Signed-off-by: Stefano Garzarella <[email protected]>

Author: dependabot[bot]

vhost-user-backend/Cargo.toml

@@ -23,7 +23,7 @@ vm-memory = { workspace = true, features = ["backend-mmap", "backend-atomic", "b
 vmm-sys-util = { workspace = true }
 
 [dev-dependencies]
-nix = { version = "0.29", features = ["fs"] }
+nix = { version = "0.30", features = ["fs"] }
 uuid = { version = "1.8.0", features=["v4"] }
 vhost = { path = "../vhost", version = "0.13.0", features = ["test-utils", "vhost-user-frontend", "vhost-user-backend"] }
 vm-memory = { workspace = true, features = ["backend-mmap", "backend-atomic"] }

vhost-user-backend/tests/vhost-user-server.rs

@@ -1,4 +1,3 @@
-use std::ffi::CString;
 use std::fs::File;
 use std::io::Result;
 use std::os::unix::io::AsRawFd;
@@ -166,11 +165,7 @@ fn vhost_user_client(path: &Path, barrier: Arc<Barrier>) {
     frontend.set_protocol_features(proto).unwrap();
     assert!(proto.contains(VhostUserProtocolFeatures::REPLY_ACK));
 
-    let memfd = nix::sys::memfd::memfd_create(
-        &CString::new("test").unwrap(),
-        nix::sys::memfd::MemFdCreateFlag::empty(),
-    )
-    .unwrap();
+    let memfd = nix::sys::memfd::memfd_create("test", nix::sys::memfd::MFdFlags::empty()).unwrap();
     let file = File::from(memfd);
     file.set_len(0x100000).unwrap();
     let file_offset = FileOffset::new(file, 0);