chore(deps): update headers requirement from 0.3 to 0.4

Updates the requirements on [headers](https://github.com/hyperium/headers) to permit the latest version.
- [Commits](hyperium/headers@headers-v0.3.0...headers-v0.3.9)

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

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

Cargo.toml

@@ -42,7 +42,7 @@ fastrand = "2"
 form_urlencoded = "1"
 futures-channel = "0.3"
 futures-util = { version = "0.3", default-features = false }
-headers = "0.3"
+headers = "0.4"
 http = "0.2"
 http-body-util = "0.1.0-rc.3"
 hmac = "0.12"