Changes are wrapped by feature flag jupyter_clean_diff.

On the commit folder, when detecting a ipynb file, creates a new diff
of those files after converting them to markdown, using the [ipynbdiff
gem](https://gitlab.com/gitlab-org/incubation-engineering/mlops/rb-ipynbdiff)

There are performance and architectural concerns on whether the rails
app is the right place for this type of diffing, but since we currently
don't have a good solution we are discussing possible alternatives for
the future here: https://gitlab.com/gitlab-org/gitlab/-/issues/342143.

Changelog: added
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/71477
Epic: https://gitlab.com/groups/gitlab-org/-/epics/6589