Removing Delegation Backend unit test and reference to container image

[SanabriaRusso]

Explain your changes:

• Removed non required test's Dhall and container reference from Buildkite's Constants.
• The Container image was removed from the registry.

Explain how you tested your changes:

• A successful CI run is expected

Checklist:

• Dependency versions are unchanged
  • Notify Velocity team if dependencies must change in CI
• Modified the current draft of release notes with details on what is completed or incomplete within this project
• Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• All tests pass (CI will check this if you didn't)
• Serialized types are in stable-versioned modules
• Does this close issues? List them

• Closes #0000

[mrmr1993]

!ci-build-me

[mrmr1993]

!ci-build-me