[Doc] Backport Tree's doc

[erwanMarmelab]

Problem

ra-tree's doc was updated about this:

Support recordRepresentation defined at resource level, and keep titleField to override it for Tree, TreeWithDetails, TreeInput

Solution

Backport it

Additional Checks

• The PR targets master for a bugfix or a documentation fix, or next for a feature
• [ ] The PR includes unit tests (if not possible, describe why)
• [ ] The PR includes one or several stories (if not possible, describe why)
• The documentation is up to date