Use %{bash_completions_dir} instead of shelling out to pkg-config
    
    bash-completion.pc was moved into bash-completion-devel:
    
    https://src.fedoraproject.org/rpms/bash-completion/c/d1f5dc48c0440cc68efdd519b78fccca416cad94
    
    Instead of adding a new dependency, use the documented macro with the same value.
    
    We also use the macro in %files. No need to co-won the directory,
    it is owned by filesystem package.
    
    [skip changelog]