convert GPLv3+ license to SPDX

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

4th.spec

@@ -1,9 +1,10 @@
 Name:           4th
 Version:        3.62.5
-Release:        17%{?dist}
+Release:        18%{?dist}
 Summary:        A Forth compiler
 
-License:        GPLv3+
+# Automatically converted from old format: GPLv3+ - review is highly recommended.
+License:        GPL-3.0-or-later
 URL:            https://thebeez.home.xs4all.nl/4tH/
 Source0:        https://downloads.sourceforge.net/project/forth-4th/%{name}-%{version}/%{name}-%{version}-unix.tar.gz
 
@@ -71,6 +72,9 @@ cp -ap sources/include/*.h %{buildroot}%{_includedir}/%{name}/
 
 
 %changelog
+* Thu Jul 25 2024 Miroslav Suchý <msuchy@redhat.com> - 3.62.5-18
+- convert license to SPDX
+
 * Wed Jul 17 2024 Fedora Release Engineering <releng@fedoraproject.org> - 3.62.5-17
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_41_Mass_Rebuild