Update nix requirement from 0.24.1 to 0.25.0

Updates the requirements on [nix](https://github.com/nix-rust/nix) to permit the latest version.
- [Release notes](https://github.com/nix-rust/nix/releases)
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](nix-rust/nix@v0.24.1...v0.25.0)

---
updated-dependencies:
- dependency-name: nix
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Diff for: xtask/Cargo.toml

@@ -11,7 +11,7 @@ clap = { version = "3.2.1", features = ["derive"] }
 fatfs = { git = "https://github.com/rafalh/rust-fatfs.git", rev = "87fc1ed5074a32b4e0344fcdde77359ef9e75432" }
 fs-err = "2.6.0"
 mbrman = "0.4.2"
-nix = "0.24.1"
+nix = "0.25.0"
 regex = "1.5.4"
 serde_json = "1.0.73"
 tempfile = "3.2.0"