Remove obsolete Group tag

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

libpng.spec

@@ -4,7 +4,6 @@ Epoch:         2
 Version:       1.6.35
 Release:       1%{?dist}
 License:       zlib
-Group:         System Environment/Libraries
 URL:           http://www.libpng.org/pub/png/
 
 Source0:       https://github.com/glennrp/%{name}/archive/v%{version}/%{name}-%{version}.tar.gz
@@ -28,7 +27,6 @@ files.
 
 %package devel
 Summary:       Development tools for programs to manipulate PNG image format files
-Group:         Development/Libraries
 Requires:      %{name}%{?_isa} = %{epoch}:%{version}-%{release}
 Requires:      zlib-devel%{?_isa} pkgconfig%{?_isa}
 
@@ -42,7 +40,6 @@ the libpng package.
 
 %package static
 Summary:       Static PNG image format file library
-Group:         Development/Libraries
 Requires:      %{name}-devel%{?_isa} = %{epoch}:%{version}-%{release}
 
 %description static
@@ -52,7 +49,6 @@ necessary for some boot packages.
 
 %package tools
 Summary:       Tools for PNG image format file library
-Group:         Development/Libraries
 Requires:      %{name}%{?_isa} = %{epoch}:%{version}-%{release}
 
 %description tools