Both the gateway doc and the tmpfiles comment said "a directory without
the sticky bit lets any user unlink files in it". True of the old 0777,
but it names the wrong lever: write permission on a directory is what
confers the right to unlink its entries, and the sticky bit is only a
restraint on that -- it was never set here, so it is not what 0751
changes. Dropping o=w removes the permission outright.
The fix is unchanged; this is so a future reader doesn't go looking for
a sticky bit that was never there. Caught in review by argus.
c5cd8f2ac4