Bump toml from 0.5.9 to 0.7.6

Bumps [toml](https://github.com/toml-rs/toml) from 0.5.9 to 0.7.6.
- [Commits](https://github.com/toml-rs/toml/commits/toml-v0.7.6)

---
updated-dependencies:
- dependency-name: toml
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

CHANGELOG.md

@@ -14,7 +14,7 @@ Unreleased
 - Bumped `libc` dependency to `0.2.159`
 - Bumped `serde` dependency to `1.0.147`
 - Bumped `structopt` dependency to `0.3.26`
-- Bumped `toml` dependency to `0.5.9`
+- Bumped `toml` dependency to `0.7.6`
 
 
 0.4.1

Cargo.lock

@@ -75,7 +75,7 @@ default-features = false
 version = "1.5.5"
 
 [dependencies.toml]
-version = "0.5.6"
+version = "0.7.6"
 
 [dev-dependencies.nitrokey-test]
 version = "0.5"

Cargo.toml

@@ -125,8 +125,9 @@ fn save_cache(cache: &Cache, path: &path::Path) -> anyhow::Result<()> {
     fs::create_dir_all(parent).context("Failed to create cache parent directory")?;
   }
   let mut f = fs::File::create(path).context("Failed to create cache file")?;
-  let data = toml::to_vec(cache).context("Failed to serialize cache")?;
-  f.write_all(&data).context("Failed to write cache file")?;
+  let data = toml::to_string(cache).context("Failed to serialize cache")?;
+  f.write_all(data.as_bytes())
+    .context("Failed to write cache file")?;
   Ok(())
 }