Update sev requirement (#519)

Updates the requirements on [sev](https://github.com/virtee/sev) to permit the latest version.

Updates `sev` to 7.0.0
- [Release notes](https://github.com/virtee/sev/releases)
- [Commits](https://github.com/virtee/sev/commits)

---
updated-dependencies:
- dependency-name: sev
  dependency-version: 7.0.0
  dependency-type: direct:production
  dependency-group: rs-dependencies
...

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Author: dependabot[bot]

scripts/attestation_policy/Cargo.toml

@@ -9,5 +9,5 @@ edition = "2021"
 clap = { version = "4.0", features = ["derive"] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-sev = "6.2.1"
+sev = "7.1.0"
 base64 = "0.22.1"