[4.0.0-rc.6] filters.external.addMask for a text object seems to make it blurry

## Version
* Phaser Version: 4.0.0
* Operating system: Windows 11
* Browser: Google Chrome


## Description

Using the new filters.external.addMask for a text object seems to make it blurry.

## Additional Information

<img width="1476" height="560" alt="Image" src="https://github.com/user-attachments/assets/41848b91-0e95-4752-8996-3532290175a0" />
