Add citations with publicationDate

[andrewheard]

Updated the citations examples (unary and streaming) to include a citation with a publicationDate.

[github-actions]

Coverage Diff

GenerateContentResponse: 43
| candidates: 38
| | citationMetadata: 4
| | | citations: 4
| | | | publicationDate: 0 -> 2 ✅
| | | | | day: 0 -> 2 ✅
| | | | | month: 0 -> 2 ✅
| | | | | year: 0 -> 2 ✅
Total Coverage: 41.43% -> 44.29% ✅

Legend:
✅ : total coverage increase
🔵 : files number increase, total coverage unaffected
🟡 : files number decrease, total coverage unaffected
❌ : total coverage decrease

[andrewheard]

Note: The failing JS Unit Test is pre-existing (firebase/firebase-js-sdk#8566). The citations tests are still passing.