no cdn support for theia-rhel8 image in quay

While https://codeready-workspaces-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/view/CRW_CI/view/Pipelines/job/crw-theia_master/ is green, it seems something is amiss with the brew integration part downstream as:

https://codeready-workspaces-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/get-sources-rhpkg-container-build/4278/console did not successfully build a container in brew.

This means we're currently stuck on Che Theia 7.14.1 (we should be on 7.14.3).