bug(form-field): NVDA reads error message twice when required marker is hidden

### Description

When the hide required marker option is turned on, NVDA reads the Form Field error message twice

### Reproduction

https://material.angular.dev/components/form-field/overview#form-field-label

### Expected Behavior

Error message is read out once

### Actual Behavior

Error message is read out twice

### Environment

- Angular: v21
- CDK/Material: v21
- Browser(s): Google Chrome with NVDA on
- Operating System (e.g. Windows, macOS, Ubuntu): Windows

从 https://material.angular.dev/components/form-field/overview#form-field-label 中表单字段标签的复现开始，并在启用隐藏必填标记选项的情况下，使用 Chrome 和 NVDA 进行复现。跟踪表单字段错误播报的行为，并验证错误消息只播报一次，而不是两次。

由索引模型根据 Issue 内容生成。