Use the recommanded way to declare the repository signing keys
The new yarn's repository signing key was not recognized via the old way to declare the key. Using the new recommanded way[1] solves the problem. It's the opportunity to migrate the declaration of the other repositories to this method.
Related to swh/infra/sysadm-environment#3120 (closed)
If we are ok with this way, perhaps we should also change the way the key of the other repositories are managed
Test Plan
docker build
Migrated from D5235 (view on Phabricator)