Consider adjusting wording for configured 'available'

[korydraughn]

See the sentence which uses the phrase configured 'available' and consider rephrasing it so that it's clearer.

irods_docs/docs/plugins/pluggable_authentication.md

Line 5 in d827723

By default, iRODS uses a secure password system for user authentication. The user passwords are scrambled and stored in the iCAT database. Additionally, iRODS supports user authentication via PAM (Pluggable Authentication Modules), which can be configured to support many things, including the LDAP or Active Directory (AD) authentication systems. GSI and Kerberos are also available. PAM and SSL have been configured 'available' out of the box with iRODS, but there is still some setup required to configure an installation to communicate with your external authentication server of choice.