Bump cppfront from 2ea1950 to 16686c1

Bumps [cppfront](https://github.com/hsutter/cppfront) from `2ea1950` to `16686c1`.
- [Release notes](https://github.com/hsutter/cppfront/releases)
- [Commits](hsutter/cppfront@2ea1950...16686c1)

---
updated-dependencies:
- dependency-name: cppfront
  dependency-type: direct:production
...

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