Restored site header text in password reset view.

It's the one shown when the optional integration described in
https://docs.djangoproject.com/en/dev/ref/contrib/admin/#adding-a-password-reset-feature
is used.

Follow-up to commits 6f470650d0 and 1d42a86ec7, together they fix
different small UI regressions after a962286b74.

Refs #21293.