Bump third_party/googletest from 6b63c98 to c875c4e

Bumps [third_party/googletest](https://github.com/google/googletest) from `6b63c98` to `c875c4e`.
- [Release notes](https://github.com/google/googletest/releases)
- [Commits](google/googletest@6b63c98...c875c4e)

---
updated-dependencies:
- dependency-name: third_party/googletest
  dependency-type: direct:production
...

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