Bump marshmallow from 3.26.1 to 4.0.0 in /flowmachine

Bumps [marshmallow](https://github.com/marshmallow-code/marshmallow) from 3.26.1 to 4.0.0.
- [Changelog](https://github.com/marshmallow-code/marshmallow/blob/dev/CHANGELOG.rst)
- [Commits](marshmallow-code/marshmallow@3.26.1...4.0.0)

---
updated-dependencies:
- dependency-name: marshmallow
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]