Install bash-completion in default location
    
    The desired location for bash-complete files is no longer in /etc.  Use
    the recently added macros from redhat-rpm-config¹ to get the path.
    
    Shorten the install command by using the completion file from the source
    directory instead of the %buildroot copy.
    
    ¹ https://src.fedoraproject.org/rpms/redhat-rpm-config/c/483a3b8 (Add
      macros.shell-completions, 2022-06-25)