Bump soft_timeout of Wait_condition.blocks_to_be_produced in integration tests

[mrmr1993]

This PR increases the soft-timeout used when waiting for some number of blocks to be produced. To quote the new comment in the code:

      (* We add 1 here to make sure that we see the entirety of at least 2*n
         full slots, since slot time may be misaligned with wait times after
         non-block-related waits.
         This ensures that low numbers of blocks (e.g. 1 or 2) have a
         reasonable probability of success, reducing flakiness of the tests.
      *)

Checklist:

• 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

[QuiteStochastic]

looks good, just make sure this gets merged to compatible as well

[mrmr1993]

looks good, just make sure this gets merged to compatible as well

good catch, I'll redirect this at compatible and merge on up from there