Update dependency django-pipeline to v3.1.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
django-pipeline	==3.0.0 -> ==3.1.0

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Release Notes

jazzband/django-pipeline (django-pipeline)

### [`v3.1.0`](https://togithub.com/jazzband/django-pipeline/blob/HEAD/HISTORY.rst#310) [Compare Source](https://togithub.com/jazzband/django-pipeline/compare/3.0.0...3.1.0) \===== - Replace deprecated .warn method with .warning - Update sourcemap paths when concatenating source files - Ensure correct compiler error styling and strip ANSI escape sequences

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