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):

Comienza con el ejemplo de mensajes de error de Angular Material form-field enlazado en el informe y reproduce el comportamiento usando NVDA, centrándote en los errores que se muestran cuando el campo pierde el foco. Compara los anuncios con la lectura única esperada e identifica la ruta de presentación de errores de form-field implicada; el trabajo estará terminado cuando mat-error se anuncie una sola vez sin producir regresiones en el comportamiento documentado.

Escrito por el modelo de indexación a partir del texto del issue.