cleanup in open_auth_file

I was looking at the following commit:

commit efc981627a723d91e86865fb363d793282e473d1
Author: Michael Paquier <michael@paquier.xyz>
Date:   Thu Nov 24 08:21:55 2022 +0900

    Rework memory contexts in charge of HBA/ident tokenization

I think when the file cannot be opened, the context should be deleted.

Please see attached patch.

I also modified one comment where `deleted` would be more appropriate verb for the context.

Cheers