python: remove all APIv2 code
    
    According to the deprecation schedule
    https://fedora-copr.github.io/posts/EOL-APIv1-APIv2
    
    we just took the following step:
    
    > September 2021 - Remove APIv2 from python3-copr library.
    
    If you cannot migrate to APIv3 yet, you can still send requests to
    APIv2 endpoints directly, without using the python3-copr library, or
    you can temporarily freeze on `python-copr-1.112`.
    
    Please don’t put aside the migration of your code for much longer. In
    April 2022 the APIv2 is going to be dropped from the frontend and the
    Copr service will no longer understand APIv2 calls.