Remove obsolete Group tag

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

libao.spec

@@ -2,7 +2,6 @@ Name:           libao
 Version:        1.2.0
 Release:        13%{?dist}
 Summary:        Cross Platform Audio Output Library
-Group:          System Environment/Libraries
 License:        GPLv2+
 URL:            http://xiph.org/ao/
 Source0:        http://downloads.xiph.org/releases/ao/%{name}-%{version}.tar.gz
@@ -21,7 +20,6 @@ using a simple API on a wide variety of platforms.
 
 %package        devel
 Summary:        Development files for %{name}
-Group:          Development/Libraries
 Requires:       %{name}%{?_isa} = %{version}-%{release}
 
 %description devel