Improvements for D11085

Summary:
In D11085, I attempted to fix this although I did so poorly. The intention was to format JSON as follows:

{
  "foo": "bar",
  "foobarbaz": []
}

But instead I had achieved this:

{
  "foo"      : "bar",
  "foobarbaz": []
}

Test Plan: Ran ./scripts/update_compat_info.php and inspected ./resources/php_compat_info.json.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11094