Bump code/common/libs/eigen from 21ae2af to 8d9f467

Bumps [code/common/libs/eigen](https://gitlab.com/libeigen/eigen) from `21ae2af` to `8d9f467`.
- [Release notes](https://gitlab.com/libeigen/eigen/tags)
- [Commits](https://gitlab.com/libeigen/eigen/compare/21ae2afd4edaa1b69782c67a54182d34efe43f9c...8d9f467036ccbc1cb9a07def2144afa81f516f83)

---
updated-dependencies:
- dependency-name: code/common/libs/eigen
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>