Remove "set password" from bin/accountadmin and let bin/auth recover recover anyone

Summary:
Ref T13043. This cleans some things up to prepare for moving account passwords to shared infrastructure.

Currently, the (very old, fairly unusual) bin/accountadmin tool can set account passwords. This is a bit weird, generally not great, and makes upgrading to shared infrastructure more difficult. Just get rid of this to simplify things. Many installs don't have passwords and this is pointless and unhelpful in those cases.

Instead, let bin/auth recover recover any account, not just administrator accounts. This was a guardrail against administrative abuse, but it has always seemed especially flimsy (since anyone who can run the tool can easily comment out the checks) and I use this tool in cluster support with some frequency, occasionally just commenting out the checks. This is generally a better solution than actually setting a password on accounts anyway. Just get rid of the check and give users enough rope to shoot themselves in the foot with if they truly desire.

Test Plan:

• Ran bin/accountadmin, didn't get prompted to swap passwords anymore.
• Ran bin/auth recover to recover a non-admin account.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13043

Differential Revision: https://secure.phabricator.com/D18901