Doc: 📝 Bump up the rocqnavi version

[yoshihiro503]

Motivation for this change

We will update the version of Rocqnavi used to generate documentation via make html.

This will add the following feature to the documentation:

• The graph on the homepage can now be zoomed in on
• The graph on the homepage can now be downloaded as an SVG file
• Code blocks within Markdown comments are now syntax-highlighted

Furthermore, we will ensure that we always use the latest version of Rocqnavi going forward.

Checklist

• added corresponding entries in CHANGELOG_UNRELEASED.md

• added corresponding documentation in the headers

Reference: How to document

Merge policy

As a rule of thumb:

• PRs with several commits that make sense individually and that
  all compile are preferentially merged into master.
• PRs with disorganized commits are very likely to be squash-rebased.

Reminder to reviewers

• Read this Checklist
• Put a milestone if possible
• Check labels