chore(doc): add missing doc for a data breaking change

[nsarlin-zama]

closes: please link all relevant issues

PR content/description

CompactFheIntX, CompactFheUintX, CompactFheIntXList, and CompactFheUintXList are also data breaking change since they no longer exist on 0.7. This adds a section in the doc to explain how they can be loaded.

Check-list:

• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)
• [ ] Relevant issues are marked as resolved/closed, related issues are linked in the description
• [ ] Check for breaking changes (including serialization changes) and add them to commit message following the conventional commit specification

[IceTDrinker]

good to merge once required checks are green 👍