Update Pipeline Stage READMEs

There are a few READMEs in the pipeline that needs to be updated.

Stage	Reason
Import Artifacts	Add Auth Example to provided code snippet
Scan Artifacts	Update to reflect use of av-updater project artifact, which replaced the use of running freshclam within each pipeline run
Build	Remove reference to use of isolated runner and update with current config and update Dockerfile ARG example to use dso.mil

Acceptance Criteria

• All required edits have been made