fix showAsModal settings modal

After the change to the schema settings #49, using the `PropKeyEditorObjectFieldTemplate` causes issues in the settings modal for the showAsModal feature, where options don't have correct margins. The `propKeyCollapse` class in said template is removing unwanted bottom margins, but since the modal is rendered inside this template, each of the fields inside the modal is in some way considered a `Collapse` element and therefore is having its margins removed. It's a bit tricky, so it needs more investigation.