build(deps): bump log from 0.4.20 to 0.4.21

Bumps [log](https://github.com/rust-lang/log) from 0.4.20 to 0.4.21.
- [Release notes](https://github.com/rust-lang/log/releases)
- [Changelog](https://github.com/rust-lang/log/blob/master/CHANGELOG.md)
- [Commits](rust-lang/log@0.4.20...0.4.21)

---
updated-dependencies:
- dependency-name: log
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Cargo.lock

@@ -13,7 +13,7 @@ publish = false
 [dependencies]
 env_logger = "^0.10.1"
 futures = "^0.3.30"
-log = "^0.4.20"
+log = "^0.4.21"
 prost = "^0.11"
 structopt = "^0.3.26"
 tink-aead = "^0.2"