chore(firebaseai): setup for mock response e2e test #2363

Job	Run time
web-wasm (tests)	4m 5s
web-app-check	3m 54s
web-wasm (packages/cloud_firestore/cloud_firestore/example)	4m 32s
web (tests)	4m 22s
web (packages/cloud_firestore/cloud_firestore/example)	3m 36s
web (tests)	3m 38s
web-app-check	3m 54s
web-wasm (packages/cloud_firestore/cloud_firestore/example)	4m 32s
web (packages/cloud_firestore/cloud_firestore/example)	3m 36s
web-wasm (tests)	4m 5s
	40m 14s

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