Revert "feed.http-hooks" HTTP request construction to use "http_build_query()" so nested "storyData" is handled correctly

Summary:
See https://discourse.phabricator-community.org/t/storydata-is-blank-in-outgoing-requests-to-the-configured-feed-http-hooks/2366/.

This behavior was changed by D20049. I think it's generally good that we not accept/encode nested values in a PHP-specific way, but retain feed.http-hooks compatibility for now.

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20114