Ensure container job uses a non latest version tag

Error: Container job does not use a non latest version tag
Bridgecrew Policy ID: BC_REPO_AZURE_PIPELINES_1
Checkov Check ID: CKV_AZUREPIPELINES_1
Severity: LOW

Ensure the containers used in your pipelines have a defined version or a digest.

-  container: ubuntu
+  container: ubuntu@sha256:817cfe4672284dcbfee885b1a66094fd907630d610cab329114d036716be49ba