Fix DataStream test timeout

[Abacn]

Datastream finalizes and rotates GCS files every 60 seconds, triggering GCS OBJECT_FINALIZE Pub/Sub notifications promptly so the integration test receives data and completes normally without hitting the condition check or test timeouts.

[codecov]

Codecov Report

❌ Patch coverage is 94.28571% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.89%. Comparing base (9d8862d) to head (db7dd03).
⚠️ Report is 33 commits behind head on main.

Files with missing lines	Patch %	Lines
...m/it/gcp/datastream/DatastreamResourceManager.java	94.28%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #4159      +/-   ##
============================================
- Coverage     56.21%   55.89%   -0.33%     
- Complexity     7340     7475     +135     
============================================
  Files          1126     1134       +8     
  Lines         68748    70136    +1388     
  Branches       7784     8011     +227     
============================================
+ Hits          38650    39205     +555     
- Misses        27599    28386     +787     
- Partials       2499     2545      +46     

Components	Coverage Δ
spanner-templates	84.63% <ø> (-3.00%)	⬇️
spanner-import-export	68.93% <ø> (-0.11%)	⬇️
spanner-live-forward-migration	88.66% <ø> (-0.92%)	⬇️
spanner-live-reverse-replication	81.26% <ø> (-2.45%)	⬇️
spanner-bulk-migration	89.06% <ø> (-3.24%)	⬇️
gcs-spanner-dv	87.85% <ø> (-1.06%)	⬇️

Files with missing lines	Coverage Δ
...m/it/gcp/datastream/DatastreamResourceManager.java	78.79% <94.28%> (+0.69%)	⬆️

... and 52 files with indirect coverage changes

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