When using iPad, download chart as image from dashboard yields blank file

### Bug description

Browse to a dashboard in Safari on iPad, download a chart as image from a dashboard. The resulting file has the chart title but is otherwise white/blank.

### Screenshots/recordings

_No response_

### Superset version

6.0.0

### Python version

I don't know

### Node version

I don't know

### Browser

Safari

### Additional context

Maybe not a huge priority for other since how often is someone in this situation ... but I did get a frustrated user coming to me today about it! Verified on my own iPad.

### Checklist

- [x] I have searched Superset docs and Slack and didn't find a solution to my problem.
- [x] I have searched the GitHub issue tracker and didn't find a similar bug report.
- [ ] I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.