NodeRemoveAction: Change display only if the removed node is a root node

[sukhwinder33445]

fixes #460

[Copilot]

Pull Request Overview

This PR fixes issue #460 by modifying the NodeRemoveAction class to only adjust display order when removing root nodes. Previously, the code would attempt to adjust display order for any removed node, but now it specifically checks if the removed node is a root node before performing display order adjustments.

• Adds a check to verify if the removed node is a root node before adjusting display order
• Removes unnecessary variable $oldDisplay and replaces it with $removedNodeDisplay
• Simplifies the logic by directly accessing the node's display value at the point of use

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[slalomsk8er]

Since I applied the patch I didn't get any Unbound nodes even if I used "Delete all occurrences of ...".