Bump marshmallow from 2.15.3 to 2.15.4 (#1047)
Bump marshmallow from 2.15.3 to 2.15.4 (#1047)

Bumps [marshmallow](https://github.com/marshmallow-code/marshmallow) from 2.15.3 to 2.15.4.
- [Release notes](https://github.com/marshmallow-code/marshmallow/releases)
- [Changelog](https://github.com/marshmallow-code/marshmallow/blob/dev/CHANGELOG.rst)
- [Commits](https://github.com/marshmallow-code/marshmallow/compare/2.15.3...2.15.4)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
Turbo87/skylines,Harry-R/skylines,skylines-project/skylines,Turbo87/skylines,RBE-Avionik/skylines,Turbo87/skylines,Harry-R/skylines,skylines-project/skylines,RBE-Avionik/skylines,skylines-project/skylines,RBE-Avionik/skylines,skylines-project/skylines,Harry-R/skylines,RBE-Avionik/skylines,Turbo87/skylines,Harry-R/skylines