Spec cleanup
    
    - only write the summary and description once
    - remove explicit %python_provide, not needed on F33+
      (after the python2 removal, this cannot be pushed down to F32 etc. anyway)
    - no need to create a separate subfolder for python3 without python2
    - explicitly only include commands matching rst*, not * (for safety)
    - ensure .egg-info is a directory
    - call python3 via the %python3 macro
    - select files to remove shebangs from with grep instead of an outdated list
    
    (There are no user facing changes, except couple removed shebangs, no need to rebuild.)