package/sdl2_mixer: fix license hash

b1b8d5b ("package/sdl2_mixer: bump version to 2.6.3") forgot to update
the hash of the license file.
In 2021 the file was renamed from COPYING.txt to LICENSE.txt in two
commits ([0] and [1]). The copyright year was subsequently updated for
2022 [2] and 2023 [3].
License is still Zlib - no changes there.

[0]: https://github.com/libsdl-org/SDL_mixer/commit/0f84f242643a913ba81bd6c260c39064c432afd3
[1]: https://github.com/libsdl-org/SDL_mixer/commit/371bf1575913828c46212e9220d4a4685ed66bb5
[2]: https://github.com/libsdl-org/SDL_mixer/commit/3f5a0502e0394aa967179d53e180f31cf038e032
[3]: https://github.com/libsdl-org/SDL_mixer/commit/6fdd4d469b4065ddfb701530d2ea602efaa772b2

Fixes:
 - http://autobuild.buildroot.net/results/302cbd0adc2c6190d8923b9449e26a3c519d2326

Signed-off-by: Daniel Lang <dalang@gmx.at>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/sdl2_mixer/sdl2_mixer.hash

@@ -1,3 +1,3 @@
 # Locally calculated
 sha256  7a6ba86a478648ce617e3a5e9277181bc67f7ce9876605eea6affd4a0d6eea8f  SDL2_mixer-2.6.3.tar.gz
-sha256  113727180e7956cb9718b03b41da85b63ea54743a33047071a623bf672895a10  COPYING.txt
+sha256  1852c8549e3d154687197d46abababd3e8faae035f19991b2ca850fa3a43ad57  LICENSE.txt

package/sdl2_mixer/sdl2_mixer.mk

@@ -8,7 +8,7 @@ SDL2_MIXER_VERSION = 2.6.3
 SDL2_MIXER_SOURCE = SDL2_mixer-$(SDL2_MIXER_VERSION).tar.gz
 SDL2_MIXER_SITE = http://www.libsdl.org/projects/SDL_mixer/release
 SDL2_MIXER_LICENSE = Zlib
-SDL2_MIXER_LICENSE_FILES = COPYING.txt
+SDL2_MIXER_LICENSE_FILES = LICENSE.txt
 SDL2_MIXER_INSTALL_STAGING = YES
 SDL2_MIXER_DEPENDENCIES = sdl2 host-pkgconf