Bump submodules/googletest from ff6133a to 56efe39 (#172)

Bumps [submodules/googletest](https://github.com/google/googletest) from `ff6133a` to `56efe39`.
- [Release notes](https://github.com/google/googletest/releases)
- [Commits](google/googletest@ff6133a...56efe39)

---
updated-dependencies:
- dependency-name: submodules/googletest
  dependency-version: 56efe3983185e3f37e43415d1afa97e3860f187f
  dependency-type: direct:production
...

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Author: dependabot[bot]