TouchScreenButton: Fix screen capability check

[akien-mga]

Fixes #69572.

Thanks @spatker for identifying the issue and the likely fix.

I haven't tested the change but it seems clear that the previous logic was wrong.
The code in 3.x is correct and matches what this PR restores:

if (!Engine::get_singleton()->is_editor_hint() && !OS::get_singleton()->has_touchscreen_ui_hint() && visibility == VISIBILITY_TOUCHSCREEN_ONLY)

[spatker]

Thanks for making this pull request! I have tried the same change locally, and it does fix the visibility issue, but the button is still not interactive in the emulator, just as before this fix. So that maybe a different issue.

[akien-mga]

@spatker Yeah this would only impact visibility, for actual input processing it might be a different issue. I'd suggest opening a new issue about that with a simple reproduction project for testing.

[spatker]

Seems like the input issue can be fixed by 67126ff