Bump flask-session from 0.3.2 to 0.4.0

Bumps [flask-session](https://github.com/fengsp/flask-session) from 0.3.2 to 0.4.0.
- [Release notes](https://github.com/fengsp/flask-session/releases)
- [Changelog](https://github.com/fengsp/flask-session/blob/master/CHANGES)
- [Commits](https://github.com/fengsp/flask-session/commits)

---
updated-dependencies:
- dependency-name: flask-session
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]