Update config requirement from 0.14 to 0.15

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@0.14.0...v0.15.7)

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

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

Cargo.toml

@@ -33,7 +33,7 @@ tracing-subscriber = { version = "0.3.17", features = [
     "time",
 ] }
 chrono = "0.4"
-config = { version = "0.14", features = ["preserve_order"] }
+config = { version = "0.15", features = ["preserve_order"] }
 faer = "0.19.3"
 faer-ext = { version = "0.2.0", features = ["nalgebra", "ndarray"] }
 pharmsol = "0.7.2"