Prior to this commit, our fallback HREF was using only the URL's
domain (e.g. `guides.rubyonrails.org/routing.html`) instead of the
provided URL (e.g. `https://guides.rubyonrails.org/routing.html`). This
resulted in the link resolving to
`<url-of-article>/guides.rubyonrails.org/routing.html`)
With this commit, we're using the given URL for the HREF.
An interesting side note, the Ruby on Rails guides includes an
`og:title` but not an `og:url` so we hit the fallback condition. Could
we use the given URL if `og:url` does not exist?
Fixesforem/forem#17679
0c6b6b9e62