Update dependency marshmallow to v3.20.1

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
marshmallow (changelog)	==3.19.0 -> ==3.20.1

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Release Notes

marshmallow-code/marshmallow (marshmallow)

### [`v3.20.1`](https://togithub.com/marshmallow-code/marshmallow/compare/3.20.0...3.20.1) [Compare Source](https://togithub.com/marshmallow-code/marshmallow/compare/3.20.0...3.20.1) ### [`v3.20.0`](https://togithub.com/marshmallow-code/marshmallow/compare/3.19.0...3.20.0) [Compare Source](https://togithub.com/marshmallow-code/marshmallow/compare/3.19.0...3.20.0)

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