Remove obsolete Group tag

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

libesmtp.spec

@@ -5,7 +5,6 @@ Name:           libesmtp
 Version:        1.0.6
 Release:        16%{?dist}
 License:        LGPLv2+
-Group:          System Environment/Libraries
 Source:         http://www.stafford.uklinux.net/libesmtp/%{name}-%{version}.tar.bz2
 URL:            http://www.stafford.uklinux.net/libesmtp/
 BuildRequires:  gcc
@@ -23,7 +22,6 @@ functionality is not the program's primary purpose.
 Summary: Headers and development libraries for libESMTP
 # example file is under the GPLv2+
 License: LGPLv2+ and GPLv2+
-Group: Development/Libraries
 Requires: %{name} = %{version}-%{release}, openssl-devel
 
 %description devel