Fix narrowing conversion warning/error

[Thra11]

Launch Checklist

PointAndCameraDistance is std::pair<Point<float>,float>. vec4 is std::array<double, 4>. Implicitly converting double to float generates warnings (or errors if -Werror=narrowing is set). This pull request avoids the warning by explicitly casting the double to a float.

• [x] briefly describe the changes in this PR
• [ ] include before/after visuals or gifs if this PR includes visual changes
• [ ] write tests for all new functionality
• [ ] document any changes to public APIs
• [ ] tagged @mapbox/maps-android @mapbox/maps-ios @mapbox/core-sdk if this PR adds or updates a public API
• [ ] tagged @mapbox/gl-js if this PR includes shader changes or needs a js port
• [ ] apply needs changelog label if a changelog is needed (remove label when added)

[Thra11]

Fixes #16522