Hello Carley, the page_restrictions column is no longer used within MediaWiki, see  https://phabricator.wikimedia.org/T218446  

The column is being removed from the page table, a change that is almost complete; you can track the progress of that here https://phabricator.wikimedia.org/T60674 if you are interested. You can use the page_restrictions table instead.

The Manual page you refer to will likely be updated once the schema change is complete.

Thank you,

Hannah Okwelum