[BEAM-14117, #21519] Delete vendored bytebuddy gradle build

[lukecwik]

Additional clean-up following #17317

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[lukecwik]

R: @cushon
CC: @kennknowles

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[codecov]

Codecov Report

Merging #22594 (19ef8fa) into master (c8d92b0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #22594   +/-   ##
=======================================
  Coverage   74.23%   74.23%           
=======================================
  Files         707      707           
  Lines       93301    93301           
=======================================
  Hits        69261    69261           
  Misses      22772    22772           
  Partials     1268     1268           

Flag	Coverage Δ
python	83.61% <ø> (ø)

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Impacted Files	Coverage Δ
sdks/python/apache_beam/io/source_test_utils.py	88.01% <0.00%> (-1.39%)	⬇️
...hon/apache_beam/runners/worker/bundle_processor.py	93.54% <0.00%> (-0.13%)	⬇️
...eam/runners/portability/fn_api_runner/execution.py	93.08% <0.00%> (+0.64%)	⬆️

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[lukecwik]

Run Python PreCommit