[minor] Use ByteString.EMPTY to Prevent Protobuf Version Pin to >3.19

[ankitsultana]

ByteString.empty() was added in 3.20.0. ByteString.EMPTY should be equivalent and will allow lower protobuf versions to be used.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.98%. Comparing base (59551e4) to head (d21c27c).
Report is 813 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13720      +/-   ##
============================================
+ Coverage     61.75%   61.98%   +0.22%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2554     +118     
  Lines        133233   140661    +7428     
  Branches      20636    21880    +1244     
============================================
+ Hits          82274    87182    +4908     
- Misses        44911    46847    +1936     
- Partials       6048     6632     +584     

Flag	Coverage Δ
custom-integration1	<0.01% <ø> (-0.01%)	⬇️
integration	<0.01% <ø> (-0.01%)	⬇️
integration1	<0.01% <ø> (-0.01%)	⬇️
integration2	0.00% <ø> (ø)
java-11	61.94% <ø> (+0.24%)	⬆️
java-21	61.86% <ø> (+0.24%)	⬆️
skip-bytebuffers-false	61.97% <ø> (+0.22%)	⬆️
skip-bytebuffers-true	61.83% <ø> (+34.11%)	⬆️
temurin	61.98% <ø> (+0.22%)	⬆️
unittests	61.97% <ø> (+0.22%)	⬆️
unittests1	46.42% <ø> (-0.47%)	⬇️
unittests2	27.77% <ø> (+0.04%)	⬆️

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