Comments on the Commit diff are shared between the
raw and rendered version. Allows per-file toggling.

Upgrades ipynb to 0.4.2, fixing issues with unknown
output types in notebooks.

Commit https://gitlab.com/gitlab-org/gitlab/-/commit/71a1a01
introduced improvements on performance for loading MRs
by saving the diffs on the database, but didn't account for the possi-
bility of renderable diffs. For now, we are supressing this optimization
only for renderable diffs (ipynb files only).

Changelog: added