bug(mat-error): mat-error presentation is announces twice with NVDA screen reader

### Is this a regression?

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

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

@angular/material 18.1.0 did not have this behavior

### Description

Hi,

I am using NVDA v2025.3 (latest version) for accessibility testing and have noticed that the mat-error presentation is announced twice by the screen reader.

The above example demonstrates the issue from the angular material docs:
https://material.angular.dev/components/form-field/overview#error-messages

### Reproduction

Steps to reproduce:
1. Open screen reader and set focus on an angular material mat-form-field with mat-error presented on blur
2. Tab away from the field to trigger error message presentation
3. Observe announcements and notice that mat-error text is read twice.

### Expected Behavior

mat-errors should only be announced a single time by the screen reader.

### Actual Behavior

mat-error is announced twice by the screen reader.

### Environment

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

Commencez par l’exemple de messages d’erreur Angular Material form-field lié dans le rapport et reproduisez le comportement avec NVDA, en vous concentrant sur les erreurs affichées lorsque le champ perd le focus. Comparez les annonces avec la lecture unique attendue et identifiez le chemin de présentation des erreurs de form-field concerné ; le travail est considéré comme terminé lorsque mat-error est annoncé une seule fois sans régression du comportement documenté.

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