fix: add hostname to URLs generated in email

[miketheman]

Since this email is triggered during upload, the resulting domain sent to users is broken, as it's using uploads.pypi.org which this domain doesn't support.

Signed-off-by: Mike Fiedler [email protected]

[miketheman]

Keep in mind: We're in code freeze for now, so unless this is urgent, we may not merge it until we're out of code freeze.