fix page error on profile page, closes CNVS-17479

work around an i18nliner issue wherein it tries to mutate frozen strings
https://github.com/jenseng/i18nliner/issues/9

test plan:
1. change your time zone to an IANA one via the console or API, e.g.
   "America/Denver"
2. your settings page should not asplode

Change-Id: I83b682abf7d7dbdf820b672356f0f03296088057
Reviewed-on: https://gerrit.instructure.com/45744
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Jon Jensen <jon@instructure.com>