Correct the mirror hash to reflect whats on the download server. A locally produced libubox SCM tarball was also verified to yield an identical checksum compared to the one currently on the download server. Fixes FS#1707. Fixes5dc32620c4("libubox: update to latest git HEAD") Signed-off-by: Jo-Philipp Wich <jo@mein.io> (cherry picked from commit432eaa940f)