bug(COMPONENT): docs components/tree/examples Tree with dynamic data esample FlatTreeControl deprecated

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

docs components/tree/examples Tree with dynamic data esample FlatTreeControl deprecated

### Reproduction

StackBlitz link:
Steps to reproduce:
1.
2.

### Expected Behavior

New Example Method

### Actual Behavior

FlatTreeControl is deprecated

Flat tree control. Able to expand/collapse a subtree recursively for flattened tree.

@deprecated
Use one of levelAccessor or childrenAccessor instead. To be removed in a future version.

@breaking-change — 21.0.0

### Environment

- Angular: 18
- CDK/Material:18
- Browser(s): edge
- Operating System (e.g. Windows, macOS, Ubuntu): windows

Commencez dans docs components/tree/examples et examinez l’exemple Tree with dynamic data utilisant FlatTreeControl. Remplacez l’approche obsolète par la méthode documentée levelAccessor ou childrenAccessor, puis vérifiez que l’exemple démontre toujours l’expansion et la réduction dynamiques d’un arbre plat.

Rédigé par le modèle d'indexation à partir du texte de l'issue.