Remove password rotation requirement

[wpears]

Along with #4228, and pursuant to Whitehouse memo M-22-09, the password rotation requirement should be dropped from keycloak. Outside of meeting the requirements of that memo, this will also make logging in smoother/easier quarter to quarter and year to year.

The actual work involved in this is simply removing the keycloak password policy in the admin, then trimming the password alert in the
registration template and password update template.