Remove obsolete Group tag

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

msgpack.spec

@@ -2,7 +2,6 @@ Name:		msgpack
 Version:	3.1.0
 Release:	1%{?dist}
 Summary:	Binary-based efficient object serialization library
-Group:		System Environment/Libraries
 
 License:	Boost
 URL:		http://msgpack.org
@@ -24,7 +23,6 @@ languages like JSON. But unlike JSON, it is very fast and small.
 
 %package devel
 Summary:	Libraries and header files for %{name}
-Group:		Development/Libraries
 Requires:	%{name}%{?_isa} = %{version}-%{release}
 
 %description devel