Fix flakiness insufficient replace fee

[ghost-not-in-the-shell]

Explain your changes:
Fix flakiness of the zkapps test, the timeout is added to avoid a race condition between ledger update and transaction pool update. The fix is simply to wait for a block to be produced and then wait for another 30 secs before we send out the zkApps. The reason for that is to make sure that update to the ledger and the transaction pool to be 100% synced before we sending out new zkApps. We wait 30s after a block is being produced because we want to avoid the situation that the previous "update states" zkApps being accidentally included a block before we send out the "insufficient replace fee" zkApps. A more detailed analysis of this can be find in #13854

Explain how you tested your changes:
*

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 Insufficient replace fee check flaking in zkApps test #13854

[ghost-not-in-the-shell]

!ci-build-me

[ghost-not-in-the-shell]

!ci-build-me

[georgeee]

Approved. @ghost-not-in-the-shell could you please extend Pr's description with a detailed description of how the "wait 30s" happens in preventing a race condition.