Minor issues on User accounts and Permissions topic page

API page: https://api.drupal.org/api/drupal/core%21modules%21system%21core.api.php...

Two problems on this page:

a) Near the top, there is a @sec tag that should be @section.

b) In the Defining Permissions section, there's some text that talks about the "return value". YML files do not have return values; this is left over from when it was a function implementing hook_permission(). So instead of saying "return value" it should say something like "this file defines".