Bump external/Catch2 from 506276c to 0321d2f

Bumps [external/Catch2](https://github.com/catchorg/Catch2) from `506276c` to `0321d2f`.
- [Release notes](https://github.com/catchorg/Catch2/releases)
- [Commits](catchorg/Catch2@506276c...0321d2f)

---
updated-dependencies:
- dependency-name: external/Catch2
  dependency-type: direct:production
...

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