convert GPLv2+ license to SPDX

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

virt-backup.spec

@@ -1,9 +1,10 @@
 Name:           virt-backup
 Version:        0.2.25
-Release:        12%{?dist}
+Release:        13%{?dist}
 Summary:        Backup script for libvirt managed VM
 
-License:        GPLv2+
+# Automatically converted from old format: GPLv2+ - review is highly recommended.
+License:        GPL-2.0-or-later
 URL:            https://git.fws.fr/fws/virt-backup
 Source0:        https://git.fws.fr/fws/%{name}/archive/%{name}-%{version}-1.tar.gz
 
@@ -58,6 +59,9 @@ mkdir -p %{buildroot}%{_sharedstatedir}/libvirt/backup
 
 
 %changelog
+* Fri Jul 26 2024 Miroslav Suchý <msuchy@redhat.com> - 0.2.25-13
+- convert license to SPDX
+
 * Sat Jul 20 2024 Fedora Release Engineering <releng@fedoraproject.org> - 0.2.25-12
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_41_Mass_Rebuild