Remove misguided assertion (next ledger)

[georgeee]

Problem: when next epoch ledger isn't finalized, assertion will fail

Solution: remove assertion as it becomes useless

TBD: test run with the HF unit test

Checklist:

• [x] Dependency versions are unchanged
  • Notify Velocity team if dependencies must change in CI
• [x] Modified the current draft of release notes with details on what is completed or incomplete within this project
• [x] Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• [x] Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• [x] All tests pass (CI will check this if you didn't)
• [x] Serialized types are in stable-versioned modules
• [x] Does this close issues? None

[georgeee]

!ci-build-me

[georgeee]

Superseded by https://github.com/MinaProtocol/mina/pull/15213