Update headers requirement from 0.3.2 to 0.4.0

Updates the requirements on [headers](https://github.com/hyperium/headers) to permit the latest version.
- [Commits](hyperium/headers@headers-v0.3.2...headers-v0.4.0)

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

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

Author: dependabot[bot]

opentelemetry-jaeger/Cargo.toml

@@ -23,7 +23,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 async-std = { workspace = true, optional = true }
 async-trait = { workspace = true }
 base64 = { version = "0.21.0", optional = true }
-headers = { version = "0.3.2", optional = true }
+headers = { version = "0.4.0", optional = true }
 http = { workspace = true, optional = true }
 hyper = { workspace = true, features = ["client"], optional = true }
 hyper-tls = { version = "0.5.0", default-features = false, optional = true }