chore(deps): upgrade integration test dependencies to reduce deprecations

[inlined]

Security Audit & Remediation: firebase-functions integration tests

A. Previous CVEs

• Resolves multiple transitive deprecation warnings and subdependency vulnerabilities from old packages:
  • glob@8.1.0 (inflight@1.0.6)
  • @google-cloud/pubsub@^2.10.0
  • firebase-admin@^10.0.0

B. Changes Made

• Upgraded @google-cloud/pubsub from ^2.10.0 to ^4.8.0 in integration_test/package.json.template.
• Upgraded firebase-admin from ^10.0.0 to ^12.0.0 in integration_test/run_tests.sh.
• These changes modernize the test harness dependencies to align with current supported versions and eliminate older deprecated transitive trees (e.g. older uuid, glob, lodash helper packages).

C. Remaining CVEs

• None.

D. Introduced CVEs

• None.

E. Testing Strategy

• Verified build and unit tests pass successfully.
• Executed lint checks.

Release Notes

relnote: chore: upgrade integration test dependencies to reduce deprecations

[gemini-code-assist]

Code Review

This pull request updates the @google-cloud/pubsub dependency version in the integration test template and bumps a version argument in the test runner script. The review feedback suggests double-quoting variable expansions in the Bash script to prevent word splitting and globbing.