Bump rdf from 3.1.1 to 3.1.2 (#13926)

Bumps [rdf](https://github.com/ruby-rdf/rdf) from 3.1.1 to 3.1.2.
- [Release notes](https://github.com/ruby-rdf/rdf/releases)
- [Changelog](https://github.com/ruby-rdf/rdf/blob/develop/CHANGES.md)
- [Commits](https://github.com/ruby-rdf/rdf/compare/3.1.1...3.1.2)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>