Un-hide the file attachments form

Here's the conservative approach that just does this for documentation.

dww asked about the origin of this code, and it came from #379072: Attachments are Disabled on Book Pages. The intent was to limit file uploads to only the docs team, since only the docs team has access to the input format to post images. However, now that this restriction has been lifted, it makes sense to lift it for everyone else.

The patch doesn't have enough context to adequately eyeball, so here's the entire relevant chunk of code:

function drupalorg_form_alter(&$form, $form_state, $form_id) {
 ...
  // List of forms to check for overrides, and the corresponding permissions.
  $override_forms = array(
    'book_node_form' => 'revert revisions',
    'forum_node_form' => 'administer nodes',
    'page_node_form' => 'administer nodes',
    'story_node_form' => 'administer nodes',
  );

  // Override the access for attachments if it's a forbidden form,
  // and the user does not have sufficient permissions.
  if (in_array($form_id, array_keys($override_forms)) && !user_access($override_forms[$form_id])) {
    if (isset($form['attachments']['#access'])) {
      $form['attachments']['#access'] = FALSE;
    }
  }
  ...
}