Merge Flatpak-specific patches

[flathub/net.ankiweb.Anki](https://github.com/flathub/net.ankiweb.Anki) applies some source patches to do things such as disabling the update check. We should merge the patches here so we don't have to track diffs. Refer to `aqt.utils.running_in_sandbox()`.

Start by reviewing the source patches in flathub/net.ankiweb.Anki and then inspect aqt.utils.running_in_sandbox(). Done means the Flatpak-specific behavior is handled in Anki so the Flathub package no longer needs to track those source diffs.

Written by the indexing model from the issue text.