Bump flat-cache from 6.1.4 to 6.1.6

Bumps [flat-cache](https://github.com/jaredwray/cacheable/tree/HEAD/packages/flat-cache) from 6.1.4 to 6.1.6.
- [Release notes](https://github.com/jaredwray/cacheable/releases)
- [Commits](https://github.com/jaredwray/cacheable/commits/HEAD/packages/flat-cache)

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

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Author: dependabot[bot]