Bump @maplibre/maplibre-gl-style-spec from 20.3.1 to 20.4.0

Bumps [@maplibre/maplibre-gl-style-spec](https://github.com/maplibre/maplibre-gl-style-spec) from 20.3.1 to 20.4.0.
- [Release notes](https://github.com/maplibre/maplibre-gl-style-spec/releases)
- [Changelog](https://github.com/maplibre/maplibre-style-spec/blob/main/CHANGELOG.md)
- [Commits](maplibre/maplibre-style-spec@v20.3.1...v20.4.0)

---
updated-dependencies:
- dependency-name: "@maplibre/maplibre-gl-style-spec"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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