Bump Submodules/AMReX-Hydro from 681640d to 3ab9864 (#420)

Bumps [Submodules/AMReX-Hydro](https://github.com/AMReX-Fluids/AMReX-Hydro) from `681640d` to `3ab9864`.
- [Commits](AMReX-Fluids/AMReX-Hydro@681640d...3ab9864)

---
updated-dependencies:
- dependency-name: Submodules/AMReX-Hydro
  dependency-type: direct:production
...

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