Make schema directory in tarball attached to the GitHub release writable

[ArturWieczorek]

Schema directory in tarball for 13.6.0.5 has a read-only permissions (dr-xr-xr-x)

artur@workstation:~/Downloads$ ll
drwxr-xr-x artur artur 4.0 KB Tue Mar 18 21:12:27 2025  bin                                   --
dr-xr-xr-x artur artur 4.0 KB Tue Mar 18 21:12:27 2025  schema                                --

The read-only schema directory causes "Permission denied" errors in some of our automated scripts.
While we can use chmod as a temporary workaround in CI, it would be better to fix the permissions in the archive itself. This will prevent others from encountering the same problem.