Remove unused relprefix and prerel macros that break rpmdev-bumpspec logic
    
    During mass rebuilds NVR is bumped by rpmdev-bumpspec. But it can't
    handle complex Release: fields such as ours, that has  %{prerel} and
    %{relprefix} macros. It adds .1 after the %{dist} macro instead of
    increasing the release number.
    The issue for rpmdev-bumpspec is unsolved since 2012:
    https://pagure.io/rpmdevtools/issue/18
    
    These macros are unused by us and only cause issues when NVR is bumped.
    So let's remove them.