Bump mods/basic_materials from `d9e0698` to `8631a26`

Bumps [mods/basic_materials](https://github.com/mt-mods/basic_materials) from `d9e0698` to `8631a26`.
- [Release notes](https://github.com/mt-mods/basic_materials/releases)
- [Commits](https://github.com/mt-mods/basic_materials/compare/d9e06980d33ec02c2321269f47ab9ec32b36551f...8631a2670bbca0bf8dbc5c128cdf8cde02fbda52)