Add missing FirstOrdinalSerializer to enum

[rlazo]

It's only necessary on enums we receive from the backend, not from the ones we send.

[github-actions]

Release note changes

No release note changes were detected. If you made changes that should be
present in the next release, ensure you've added an entry in the appropriate
CHANGELOG.md file(s).

[google-oss-bot]

	1 Warning
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[google-oss-bot]

Coverage Report ¹

Affected Products

No changes between base commit (bd157db) and merge commit (bd39730).

Test Logs

• Merge (bd39730): https://github.com/firebase/firebase-android-sdk/actions/runs/11017269758

1. https://storage.googleapis.com/firebase-sdk-metric-reports/7AgPxB8wRd.html

[github-actions]

Unit Test Results

  16 files  ±0    16 suites  ±0   14s ⏱️ -1s
107 tests  - 1  107 ✔️  - 1  0 💤 ±0  0 ❌ ±0 
214 runs   - 2  214 ✔️  - 2  0 💤 ±0  0 ❌ ±0 

Results for commit afd9c71. ± Comparison against base commit bd157db.

This pull request removes 1 test.

com.google.firebase.vertexai.common.UnarySnapshotTests ‑ code execution parses correctly

♻️ This comment has been updated with latest results.

[google-oss-bot]

Size Report ¹

Affected Products

• firebase-vertexai

  Type	Base (bd157db)	Merge (bd39730)	Diff
  aar	487 kB	464 kB	-23.0 kB (-4.7%)
  apk (release)	9.30 MB	9.29 MB	-13.6 kB (-0.1%)

Test Logs

• Base (bd157db): https://github.com/firebase/firebase-android-sdk/actions/runs/11017070604
• Merge (bd39730): https://github.com/firebase/firebase-android-sdk/actions/runs/11017269758

1. https://storage.googleapis.com/firebase-sdk-metric-reports/ZW1NxoIvk0.html

[daymxn]

LGTM, but 1 pending comment