Disallow to add rank in create tree dialog

[CarolineDenis]

Fixes #5376

Checklist

• Self-review the PR after opening it to make sure the changes look good
  and self-explanatory (or properly documented)
• Add relevant issue to release milestone

Testing instructions

Go to taxon tree
Click the add button next to tree name
Click any tree

• See you cannot add rank using form or table view

[pashiav]

Testing instructions

Go to taxon tree
Click the add button next to tree name
Click any tree

• See you cannot add rank using form or table view

---

Looks good! Cannot add tree def items.

[lexiclevenger]

This also disables the Add button in the Tree Def Items form for existing trees, not just when creating a new Tree Definition. Is this the expected behavior?

Screen.Recording.2024-11-06.164835.mp4

[CarolineDenis]

@lexiclevenger, yes