Bump whatlang from 0.13.0 to 0.15.0

Bumps [whatlang](https://github.com/greyblake/whatlang-rs) from 0.13.0 to 0.15.0.
- [Release notes](https://github.com/greyblake/whatlang-rs/releases)
- [Changelog](https://github.com/greyblake/whatlang-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/greyblake/whatlang-rs/compare/v0.13.0...v0.15.0)

---
updated-dependencies:
- dependency-name: whatlang
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

plume-models/Cargo.toml

@@ -25,7 +25,7 @@ tantivy = "0.13.3"
 url = "2.1"
 walkdir = "2.2"
 webfinger = "0.4.1"
-whatlang = "0.13.0"
+whatlang = "0.15.0"
 shrinkwraprs = "0.3.0"
 diesel-derive-newtype = "0.1.2"
 glob = "0.3.0"