removes unused shared/_accounts_secondary_content partial

test plan:
* regression test account views

Change-Id: I475725206f60cbde1befa0777da0123461c44c94
Reviewed-on: https://gerrit.instructure.com/29112
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Stanley Stuart <stanley@instructure.com>
Product-Review: Marc LeGendre <marc@instructure.com>
QA-Review: Marc LeGendre <marc@instructure.com>