Bump Submodules/amrex from b3f6738 to 69f1ac8 (#559)

Bumps [Submodules/amrex](https://github.com/AMReX-Codes/amrex) from `b3f6738` to `69f1ac8`.
- [Release notes](https://github.com/AMReX-Codes/amrex/releases)
- [Commits](AMReX-Codes/amrex@b3f6738...69f1ac8)

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

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