Trac: Use normalized bugs URL from package

Without this, the trac URL for jQuery UI ends up as "http://bugs.jquery-ui.com" (note the dash). This is another case where `Release.project` turns out to be invalid (didn't match npm package for QUnit, undefined/empty on Windows) - can we just remove it entirely?

I'm replacing the slash at the end since the `path` starts with a slash. In jQuery UI's package.json, the bugs URL ends with a slash, in jQuery Core it doesn't.