ruby.rpmlintrc: Ignore zero-length error for gem.build_complete file.
    
    This error is gone as false positive in rpmlint 2.0+. However the rpmlint
    version on Zuul CI running on the Fedora 34 container is still 1.11. After Zuul
    CI is upgraded to Fedora 35+ container, and uses the rpmlint 2, we can notice
    this filter is not used by "E: unused-rpmlintrc-filter" error, and remove it.