Update packaging tutorial link
    
    The creating-rpm-packages page no longer exists.  There is a page-alias
    for it, but that alias broke recently and our link didn't work for a
    period of time.  It will be more resiliant to use the direct link
    instead of relying on the alias.
    
    https://pagure.io/fedora-docs/package-maintainer-docs/issue/160
    https://pagure.io/fedora-docs/package-maintainer-docs/pull-request/155