[Broken Website] Google Docs (and Sheets) not working with Dynamic theme on Firefox and Brave

### Prerequisites

- [x] I [searched for any existing report](https://github.com/darkreader/darkreader/issues?q=is%3Aissue) about this website issue to avoid opening a duplicate.
- [x] I can reproduce this website issue in a new, unmodified web browser profile with Dark Reader installed as the only extension.

### Website Issue Description

On Google Docs, the background is made dark but the text remains black:

On Google Sheets, the menus are dark but the sheet itself is not:

In both cases, the title of the doc is also doubled and blurry.

Switching to the standard Filter theme seems to mostly resolve the issue.

### Website Address

https://docs.google.com/spreadsheets and https://docs.google.com/document

### Steps To Reproduce

1. Open a Google Doc or Google Sheet.
2. Switch to Dynamic theme for Dark Reader

### Screenshots

_No response_

### Operating System

macOS 15.7.3 and Windows 10

### Web Browser name and version

Firefox 147.0.3 (aarch64) and Brave

### Dark Reader version

4.9.120

### Additional Context

_No response_