We now have a `gitea` formula in homebrew/core and its `stable` URL
uses a dl.gitea.com tarball. Since the URL's domain is gitea.com,
livecheck tries to preprocess the URL into a `.git` URL but the
resulting URL doesn't work because it's not a Git repository.
Gitea repositories use gitea.com (with no subdomain), so
`#preprocess_url` should be comparing the URI host (`dl.gitea.com`)
instead of the domain (`gitea.com`). This change allows gitea.com
repository URLs to continue to be preprocessed into a `.git` URL
while dl.gitea.com URLs are left untouched.
This makes the same change for the other domains, as they don't use
a subdomain either.
88109b16c3