Bump flat-cache from 3.2.0 to 4.0.0

Bumps [flat-cache](https://github.com/jaredwray/flat-cache) from 3.2.0 to 4.0.0.
- [Release notes](https://github.com/jaredwray/flat-cache/releases)
- [Changelog](https://github.com/jaredwray/flat-cache/blob/master/changelog.md)
- [Commits](https://github.com/jaredwray/flat-cache/compare/v3.2.0...v4.0.0)

---
updated-dependencies:
- dependency-name: flat-cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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