flarumer1 As my host only offers PHP 7.0 it looks like i wont be able to upgrade to beta8 for some time, so im still stuck on the extension to remove the font api domain.
In general I'm not a fan of editing core files, as these changes will be removed with the next upgrade of the software. In your case however, I see no reason not to go that route, as the next upgrade will remove the need for your edit.
You may change the file vendor/flarum/core/src/Http/WebApp/WebAppView.php
, just remove the line:
$this->addHeadString('<link rel="stylesheet" href="//fonts.googleapis.com/css?family=Open+Sans:400italic,700italic,400,700,600">', 'font');
... or replace it with your own version.