Update watt requirement from 0.4 to 0.5 (#20)

Updates the requirements on [watt](https://github.com/dtolnay/watt) to permit the latest version.
- [Release notes](https://github.com/dtolnay/watt/releases)
- [Commits](dtolnay/watt@0.4.0...0.5.0)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.toml

@@ -14,5 +14,5 @@ version = "0.2.2"
 proc_macro = true
 
 [dependencies]
-watt = "0.4"
+watt = "0.5"