This triggers a bug in ListOriginContributors, causing it to include
"null" as a contributor.
A future commit will fix this.

This Java script (and related Luigi tasks) traverse the graph in
topological order, building up the set of all contributors to a
node and its ancestors, then dump the value of this set for every
origin node they encounter.

This allows readers to efficiently get ancestors of nodes with low indegree
(ie. most revisions), as it avoids a random access / API call.

It's hard to handle correctly, and it does not seem useful to use
outside the compression pipeline.

In practice, we use separate directories for this.

Encountered while compressing the 2021-03-23-popular-3k-python dataset.

- pre-commit from 4.1.0 to 4.3.0,
- codespell from 2.2.1 to 2.2.2,
- black from 22.3.0 to 22.10.0 and
- flake8 from 4.0.1 to 5.0.4. Also freeze flake8 dependencies.

Also change flake8's repo config to github (the gitlab mirror
being outdated).