Remove autostart option

[hluk]

This should be handled by a background portal instead of the app itself.

The option should be hidden/disabled in the next CopyQ release: hluk/CopyQ#2518

[flathubbot]

Started test build 76625

[flathubbot]

Build 76625 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/59210/com.github.hluk.copyq.flatpakref

[flathubbot]

Started test build 76629

[flathubbot]

Build 76629 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/59214/com.github.hluk.copyq.flatpakref

[hluk]

The option should be hidden/disabled in next CopyQ release: hluk/CopyQ#2518