license: LGPL-2.1+ -> LGPL-2.1-or-later

Follow-up for db9ecf0501.

test/sd-script.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-# SPDX-License-Identifier: LGPL-2.1+
+# SPDX-License-Identifier: LGPL-2.1-or-later
 #
 # sd-script.py: create LOTS of sd device entries in fake sysfs
 #

units/user/app.slice

@@ -1,4 +1,4 @@
-#  SPDX-License-Identifier: LGPL-2.1+
+#  SPDX-License-Identifier: LGPL-2.1-or-later
 #
 #  This file is part of systemd.
 #

units/user/background.slice

@@ -1,4 +1,4 @@
-#  SPDX-License-Identifier: LGPL-2.1+
+#  SPDX-License-Identifier: LGPL-2.1-or-later
 #
 #  This file is part of systemd.
 #

units/user/session.slice

@@ -1,4 +1,4 @@
-#  SPDX-License-Identifier: LGPL-2.1+
+#  SPDX-License-Identifier: LGPL-2.1-or-later
 #
 #  This file is part of systemd.
 #