convert GPLv2 license to SPDX

This is part of https://fedoraproject.org/wiki/Changes/SPDX_Licenses_Phase_4

R-chron.spec

@@ -7,10 +7,11 @@
 
 Name:             R-%{packname}
 Version:          2.3.60
-Release:          7%{?dist}
+Release:          8%{?dist}
 Summary:          Chronological Objects which can Handle Dates and Times
 
-License:          GPLv2
+# Automatically converted from old format: GPLv2 - review is highly recommended.
+License:          GPL-2.0-only
 URL:              https://CRAN.R-project.org/package=%{packname}
 Source0:          https://cran.r-project.org/src/contrib/%{packname}_%{packver}.tar.gz
 
@@ -70,6 +71,9 @@ _R_CHECK_FORCE_SUGGESTS_=0 %{_bindir}/R CMD check %{packname}
 
 
 %changelog
+* Mon Jul  29 2024 Miroslav Suchý <msuchy@redhat.com> - 2.3.60-8
+- convert license to SPDX
+
 * Wed Jul 17 2024 Fedora Release Engineering <releng@fedoraproject.org> - 2.3.60-7
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_41_Mass_Rebuild