Bump external/fmt in the submodules group across 1 directory (#269)

Bumps the submodules group with 1 update in the / directory: [external/fmt](https://github.com/fmtlib/fmt).


Updates `external/fmt` from `873670b` to `e3ddede`
- [Release notes](https://github.com/fmtlib/fmt/releases)
- [Commits](fmtlib/fmt@873670b...e3ddede)

---
updated-dependencies:
- dependency-name: external/fmt
  dependency-type: direct:production
  dependency-group: submodules
...

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