Bump external/fmt from 13cfaa2 to c17816c

Bumps [external/fmt](https://github.com/fmtlib/fmt) from `13cfaa2` to `c17816c`.
- [Release notes](https://github.com/fmtlib/fmt/releases)
- [Commits](fmtlib/fmt@13cfaa2...c17816c)

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

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