Fix OpenTelemetry dependencies in published POMs

[bvolpato]

Recent OpenTelemetry tracing changes added versionless opentelemetry-api dependencies to GCP and Kafka IO without importing the corresponding BOM. Their published snapshot POMs became invalid, so Maven discarded transitive dependencies and the PostRelease examples archetype failed to compile with missing Avro and GCP classes.

Import the OpenTelemetry BOM in both modules so generated POMs provide the required dependency management.

Addresses #38714.

Testing:

• Confirmed both baseline generated POMs fail mvn validate because opentelemetry-api has no version.
• Confirmed both patched generated POMs pass mvn validate and import opentelemetry-bom-alpha.
• Built GCP IO and Kafka IO jars and passed their Spotless checks.
• Deployed patched snapshots locally and confirmed the generated examples archetype compiles all 71 sources from a clean target with -Pspark-runner, matching the failing PostRelease profile.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.11%. Comparing base (a89b9f7) to head (ee3908f).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #39608      +/-   ##
============================================
- Coverage     58.15%   57.11%   -1.04%     
+ Complexity    13085     3641    -9444     
============================================
  Files          2521     1189    -1332     
  Lines        264850   191890   -72960     
  Branches      10788     3815    -6973     
============================================
- Hits         154017   109598   -44419     
+ Misses       105055    78773   -26282     
+ Partials       5778     3519    -2259     

Flag	Coverage Δ
java	72.17% <ø> (+7.90%)	⬆️

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[github-actions]

Assigning reviewers:

R: @kennknowles for label java.
R: @johnjcasey for label kafka.

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[stankiewicz]

thanks for spotting and fixing that