Fix unused import to unbreak presubmit lint.

[robertwb]

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[codecov]

Codecov Report

Merging #27447 (33037c1) into master (ca674aa) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #27447   +/-   ##
=======================================
  Coverage   71.21%   71.21%           
=======================================
  Files         862      862           
  Lines      104658   104657    -1     
=======================================
  Hits        74528    74528           
+ Misses      28582    28581    -1     
  Partials     1548     1548           

Flag	Coverage Δ
python	80.41% <ø> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
...on/apache_beam/runners/dataflow/dataflow_runner.py	83.28% <ø> (+0.22%)	⬆️

... and 2 files with indirect coverage changes

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[Abacn]

test passed on jenkins

note that recently setup github action lint test (run same gradle task) fails with

apache_beam/runners/dataflow/dataflow_runner.py:45:0: W0611: Unused beam_runner_api_pb2 imported from apache_beam.portability.api (unused-import)

unrelated. It appears the lint check is non-deterministic on different machines / runs