Upgrade to boost 1.81.0

Per the other commits, we are temporarily moving to boost 1.81.0 to get
ahead of some of the API breaking changes in boost-url.  This requires
moving CI off of using the yocto mirror.  So far as I'm aware, the boost
bandwidth issues have been long solved, so this should be fine.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Iec89a040374bef52c5188c89be9f8a25a12d6164
1 file changed