Remove obsolete Group tag

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

volpack.spec

@@ -2,7 +2,6 @@ Name:          volpack
 Version:       1.0c7
 Release:       18%{?dist}
 Summary:       Portable library for fast volume rendering
-Group:         System Environment/Libraries
 License:       BSD
 URL:           http://amide.sourceforge.net
 Source0:       http://downloads.sourceforge.net/amide/%{name}/%{name}-%{version}.tgz
@@ -18,7 +17,6 @@ produce high-quality images.
 
 %package       devel
 Summary:       Shared libraries and header files for development using volpack
-Group:         Development/Libraries
 Requires:      volpack = %{version}-%{release}
 
 %description   devel
@@ -29,7 +27,6 @@ library.
 
 %package       doc
 Summary:       Documentation and examples for help using volpack
-Group:         Documentation
 Requires:      volpack = %{version}-%{release}
 
 %description   doc