fix(deps): remediate open Dependabot security alerts

[krokoko]

Fixes open Dependabot security alerts.

Summary

Remediates 8 open Dependabot alerts by removing an unused dev dependency chain and
bumping vulnerable Python packages in lambda dev/runtime lockfiles.

• Remove unused aws-sdk-mock to eliminate transitive aws-sdk v2 (alert 163) and uuid@8.0.0 (alert 232)
• Bump pytest to >=9.0.3 in lambda dev dependencies (214, 215, 216, 230)
• Bump requests to 2.34.2 and Pygments to 2.21.0 in OpenSearch lambda lockfile (195, 208)

Pull Request Checklist

• Testing
  • Unit test added (prefer not to modify an existing test, otherwise, it's probably a breaking change)
  • Integration test added (if adding a new pattern or making a significant update to an existing pattern)
• Docs
  • README: README and/or documentation topic updated
  • Design: For significant features, design document added to design folder

Test plan

• npx projen compile
• Jest unit tests (353/353 pass; bedrock-batch-sfn suite excluded locally — requires Docker)
• Integration snapshot asserts pass
• uv run pytest in lambda/aws-bedrock-batch-stepfn (27/27 pass)
• uv lock --check in lambda/aws-bedrock-batch-stepfn
• CI build on GitHub Actions (includes Docker-based bedrock-batch-sfn tests)

Notes

• aws-sdk-mock was listed in devDependencies but had no imports anywhere in the codebase.
• Python dependency bumps are dev-only except requests (2.32.5 → 2.34.2), a runtime
  transitive dependency of opensearch-py within its existing version constraint.
• No breaking changes to construct APIs or runtime behavior.

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By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.88%. Comparing base (e12a0d0) to head (620dbc2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #1387    +/-   ##
========================================
  Coverage   94.88%   94.88%            
========================================
  Files          87       87            
  Lines       26951    26951            
  Branches      480      834   +354     
========================================
  Hits        25572    25572            
  Misses       1379     1379            

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