Revise the pagure-dist-git spec to build similarly to Pagure itself
We don't build Pagure for both Python versions, so there's no reason
to do the same for pagure-dist-git. In addition, the spec is greatly
simplified now and is compatible with Pagure instances running on Fedora
in Python 3.
Finally, the setuptools data has been updated to indicate the correct
minimum version of Pagure this is compatible with and a similar
description to what is used in the spec file.
Signed-off-by: Neal Gompa <ngompa13@gmail.com>