make-dist: don't use --continue option for wget

make-dist: don't use --continue option for wget

the boost jfrog mirror is broken and returns an HTML error page instead
of the archive. the file size of this page is 11534 bytes

when download_from() retries the download from download.ceph.com, the -c
option tells it to resume the download of the existing file. the
resulting boost_1_82_0.tar.bz2 ends up with the correct total file size
of 121325129 bytes, but the first 11534 bytes still correspond to the
HTML from jfrog. that causes the sha256sum mismatch

remove the -c option so that wget fetches the archive in its entirety

Signed-off-by: Casey Bodley <cbodley@redhat.com>