Bug 1692400: Update pip before using it r=glandium

This enables us to get a wheel for python cryptography instead of
building it ourselves, which breaks because we don't have a rust
compiler.

Differential Revision: https://phabricator.services.mozilla.com/D105060

taskcluster/docker/updatebot/privileged-setup.sh

@@ -58,6 +58,7 @@ cd /builds/worker/
 chown -R worker:worker .
 chown -R worker:worker .*
 
+python3 -m pip install -U pip
 python3 -m pip install poetry
 
 rm -rf /setup