remove dead code in pseudonym_sessions/new.html

test plan:
* regression on unsuccessful_login behavior

Change-Id: Ia26eb4abd27d0502336be2ddcaf0f7d9bfde738f
Reviewed-on: https://gerrit.instructure.com/29137
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
Product-Review: Marc LeGendre <marc@instructure.com>
QA-Review: Marc LeGendre <marc@instructure.com>