[Broken Website] desmos.com/calculator

### 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

In dark mode, the gridline is still black which reduces contrast. It should be inverted to white.

### Website Address

desmos.com/calculator

### Steps To Reproduce

1. Go to the website
2. Enable Dark Reader
3. Switch to Dark Mode

### Screenshots

_No response_

### Operating System

macOS 12.6

### Web Browser name and version

Chrome 118

### Dark Reader version

4.9.94

### Additional Context

_No response_