Support not finding the versionless package in the Maven metadata sync worker

In !55207 (merged), we created a background worker to sync the versions of maven package from the database to a new maven-metadata.xml file.

This file is hosted in a package similarly named but without a version also called the versionless package.

From the errors (internal) reported by the worker, this versionless package does not always exist.

The worker should be update to not fail when the versionless package does not exist.