Remove obsolete Group tag

References: https://fedoraproject.org/wiki/Changes/Remove_Group_Tag

rubygem-concurrent-ruby.spec

@@ -5,7 +5,6 @@ Name: rubygem-%{gem_name}
 Version: 1.0.5
 Release: 4%{?dist}
 Summary: Modern concurrency tools for Ruby
-Group: Development/Languages
 License: MIT
 URL: http://www.concurrent-ruby.com
 Source0: https://rubygems.org/gems/%{gem_name}-%{version}.gem
@@ -32,7 +31,6 @@ patterns.
 
 %package doc
 Summary: Documentation for %{name}
-Group: Documentation
 Requires: %{name} = %{version}-%{release}
 BuildArch: noarch