package/musl: fix license hash

package/musl: fix license hash

Hash of license file was not updated after bump to version 1.1.23, year
and authors were updated by:
- https://git.musl-libc.org/cgit/musl/commit/COPYRIGHT?id=7a6c8a0df1b685d788fd4d3763681bb3018806d7
- https://git.musl-libc.org/cgit/musl/commit/COPYRIGHT?id=d6dcd4185bddff34724d6d539f834e9daf7dcf3d

Fixes:
 - http://autobuild.buildroot.org/results/bbf81a9f44768894c1a55bb1bac6728aff6f2431

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>