Allow 'contributors' that can edit published handbook pages to edit them without review

[dd32]

When a user is added to a make site with any role (including the 'contributor' or 'subscriber' roles), they're granted access to edit handbook pages, including published ones.

However, if they attempt to edit the page, they're forced to 'submit for review' which unpublishes the existing page.

If the user has the 'edit_pages' capability, they're able to edit and publish handbook pages (but not actual pages).

HelpHub has a dedicated Editor role, perhaps that's needed here, or we should just let all users (other than 'subscriber'?) on a site edit all aspects of handbook pages.

See https://meta.trac.wordpress.org/browser/sites/trunk/wordpress.org/public_html/wp-content/plugins/handbook/inc/handbook.php?marks=43-71,306-327#L300