Build(deps): Bump fivefilters/readability.php from 3.1.5 to 3.1.6

Bumps [fivefilters/readability.php](https://github.com/fivefilters/readability.php) from 3.1.5 to 3.1.6.
- [Release notes](https://github.com/fivefilters/readability.php/releases)
- [Changelog](https://github.com/fivefilters/readability.php/blob/master/CHANGELOG.md)
- [Commits](fivefilters/readability.php@v3.1.5...v3.1.6)

---
updated-dependencies:
- dependency-name: fivefilters/readability.php
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>