Remove obsolete Group tag

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

rubygem-mustache.spec

@@ -4,7 +4,6 @@ Name: rubygem-%{gem_name}
 Version: 1.0.2
 Release: 7%{?dist}
 Summary: Mustache is a framework-agnostic way to render logic-free views
-Group: Development/Languages
 License: MIT
 URL: https://github.com/mustache/mustache
 Source0: https://rubygems.org/gems/%{gem_name}-%{version}.gem
@@ -30,7 +29,6 @@ template.
 
 %package doc
 Summary: Documentation for %{name}
-Group: Documentation
 Requires: %{name} = %{version}-%{release}
 BuildArch: noarch