Update config requirement from 0.14.1 to 0.15.4

Updates the requirements on [config](https://github.com/rust-cli/config-rs) to permit the latest version.
- [Changelog](https://github.com/rust-cli/config-rs/blob/main/CHANGELOG.md)
- [Commits](rust-cli/config-rs@v0.14.1...v0.15.4)

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

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

Cargo.toml

@@ -7,7 +7,7 @@ edition = "2021"
 
 [dependencies]
 chrono = { version = "0.4.38", features = ["serde"] }
-config = { version = "0.14.1", features = ["toml"] }
+config = { version = "0.15.4", features = ["toml"] }
 reqwest = { version = "0.12.9", features = ["json"] }
 rumqttc = "0.24.0"
 serde = { version = "1.0.215", features = ["derive"] }