fix: removed unused prevent click

[sabrina-bongiovanni]

The preventClick function set on all form prevents checkbox onChange to have effects.

Same issue as collective/volto-dropdownmenu#36

The problem is that the click is not applied to the component. No onChange function at any level is even triggered, which means that it is not a id problem or a onChange function problem, but the fact that the click does not trigger anything inside the component.

This does not happen on other widgets because the components (text input, buttons, etc.) intercept the click before the preventClick does as it does not propagate.
Since it seems there is actually no need for a preventClick function, I would just remove it and keep the preventEnter as it is the one that prevents the real risk of submitting the form.

I guessed preventClick was introduced to avoid any submissions of the form, but removing it does not seem to change anything besides making the Checkbox work.
We tried to

change menu item
change menu navigation tab
remove or add item menus to the same tab
remove or add tabs to the navigation tabs
changing other fields
the network tab does not show any submits nor the form seems to have any issues.