Bump 3rd_party/marian-dev from 6a6bbb6 to aa0221e (#452)

Bumps [3rd_party/marian-dev](https://github.com/browsermt/marian-dev) from `6a6bbb6` to `aa0221e`.
- [Commits](browsermt/marian-dev@6a6bbb6...aa0221e)

---
updated-dependencies:
- dependency-name: 3rd_party/marian-dev
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>