media-libs/plotutils: update LICENSE

Closes: https://bugs.gentoo.org/880287
Signed-off-by: Ulrich Müller <[email protected]>

media-libs/plotutils/plotutils-2.6-r2.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2021 Gentoo Authors
+# Copyright 1999-2024 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
@@ -9,7 +9,7 @@ DESCRIPTION="Powerful C/C++ function library for exporting 2-D vector graphics"
 HOMEPAGE="https://www.gnu.org/software/plotutils/"
 SRC_URI="mirror://gnu/plotutils/${P}.tar.gz"
 
-LICENSE="GPL-2"
+LICENSE="GPL-2+"
 SLOT="0"
 KEYWORDS="~alpha amd64 arm arm64 ~hppa ~ia64 ppc ppc64 ~riscv ~s390 sparc x86 ~amd64-linux ~x86-linux"
 IUSE="+png X"