SSO users should not be able to try to change their password

[lampwins]

Environment

• Python version: 3.8
• Nautobot version: 1.2.8

Steps to Reproduce

1. Enable SSO automatication
2. Login as an SSO user
3. Navigate to your user profile

Expected Behavior

Because I am an SSO user, I should not be presented with the ability to change my password.

Observed Behavior

The change password view is accessible and I am able to attempt a password change. This operation of course fails because no password is actually set for my user account.

[jathanism]

Looks like we'd need to update the conditional that decides whether or not that nav tab is exposed. Today it's only gated on {% if not request.user.ldap_username %}, which would only be relevant for LDAP backends.