In Webhooks, label HTTP response codes as "HTTP Status Code", not "HTTP Error"

Summary: See PHI1068. We currently show "HTTP Error - 200", which is misleading. Instead, label these results as "HTTP Status Code".

Test Plan: {F6206016}

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20148