Update D7 documentation for the new "administer software updates" permission

Since #67234: Update script access rights was recently committed (which adds an "administer software updates" permission for running update.php and therefore no longer requires you to log in as user 1 or hack setttings.php in order to update your site), @webchick pointed out that there may be a number of handbook pages that will be out of date as a result of this change.

This issue is for making sure that those handbook pages get correctly updated for Drupal 7.