fix typo in LDAP config settings

fixes CNVS-12781

test plan
 - specs should pass

Change-Id: I53aad0d08ae0cf5f81faa612f4351b993ef2c712
Reviewed-on: https://gerrit.instructure.com/34111
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>