Tor Browser defaults to a restricted folder for uploads

To reproduce:

1. Start Tails, get Tor ready.
2. Open Tor Browser
3. Edit a Redmine ticket or do something else to get to an upload form.
4. Click on Browse...
5. Result: Could not read the contents of Desktop. Permission denied.

Related issues

• Is duplicate of #8917 (closed)

Original created by @sajolida on 9334 (Redmine)