Remove unneeded form visibility scrollbars

[cconard96]

Checklist before requesting a review

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.

Description

Remove another forced scrollbar display in form editor

[orthagh]

This one requires a look from either @ccailly or @AdrienClairembault

[ccailly]

In both cases, I am unable to reproduce behavior that uses a scrollbar.
If the visibility dropdown takes up more space than is available, the scrollbar appears at the level of the entire form editor rather than on the dropdown.

In any case, there is some minor styling work to be done on the condition dropdowns.
If the target name is too long, you end up with this kind of field for entering the value (the field width is too small to see even a single character):

[cconard96]

Well removing the forced display of scrollbars and changing it to be automatic is legitimate, but there is still issues with the card never overflowing. It doesn't have a maximum width, and instead continues growing to fit-content and so it itself overflows the form editor.

[ccailly]

I think the min-width is necessary; we don't want the dropdown to be too small.
700px for the min-width seems fine to me.
In my opinion, the max-width should correspond to the available space in the form container.

[cconard96]

That isn't how it works in practice though. The dropdown panel's scroll container is the editor (.form-editor) which has overflow: auto. It will continue to grow infinitely and overflow the editor element.

The panel will never be too small because it contains a heading and 3 buttons which would keep the panel from shrinking too much. Still, we can also add a smaller min width.