Facebook App ID shouldn't be a requirement for putting in OG meta tags

Currently, articles don't get the OG meta tags if there isn't a configured `OPEN_GRAPH_FB_APP_ID`.

This PR changes the logic to match https://github.com/DandyDev/pelican-bootstrap3/commit/7a472b2f0a46265ccbc52a88741fde47783d1e03#diff-8944b57466f08564caa53a1988261ae0R31 and https://github.com/DandyDev/pelican-bootstrap3/commit/7a472b2f0a46265ccbc52a88741fde47783d1e03#diff-9cac001cb097f71f61611dfb8cccb374R5 to allow the tags to be created on an article without the `OPEN_GRAPH_FB_APP_ID`.