Bump flexsearch from 0.7.21 to 0.7.31

Bumps [flexsearch](https://github.com/nextapps-de/flexsearch) from 0.7.21 to 0.7.31.
- [Release notes](https://github.com/nextapps-de/flexsearch/releases)
- [Changelog](https://github.com/nextapps-de/flexsearch/blob/master/CHANGELOG.md)
- [Commits](https://github.com/nextapps-de/flexsearch/commits/0.7.31)

---
updated-dependencies:
- dependency-name: flexsearch
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]