Fix relaxed schema
This MR sets the tag field as required for docker resources in the relaxed hardening_manifest schema.
Successful test pipelines:
- https://repo1.dso.mil/dsop/opensource/pipeline-test-project/grafana/-/jobs/1571748
- https://repo1.dso.mil/dsop/opensource/pipeline-test-project/grafana/-/jobs/1571553
The error message in the second test pipeline is incorrect, but this is an issue with the JSONSchema validate method's error reporting.
Edited by Kenneth Maguire