Downgrade google-genai to working version

[sternakt]

Why are these changes needed?

Fixes #1236 by downgrading google-genai to 1.3.0

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ There is a different number of reports uploaded between BASE (fb0000b) and HEAD (9a356d0). Click for more details.

HEAD has 1229 uploads less than BASE

Flag	BASE (fb0000b)	HEAD (9a356d0)
3.9	82	9
ubuntu-latest	145	10
optional-deps	141	0
commsagent-telegram	9	0
3.10	96	0
commsagent-slack	9	0
commsagent-discord	9	0
3.13	85	0
core-without-llm	14	1
browser-use	7	0
macos-latest	104	0
3.11	64	1
3.12	36	0
windows-latest	114	0
jupyter-executor	9	0
retrievechat-qdrant	14	0
retrievechat-mongodb	10	0
retrievechat	15	0
websockets	9	0
interop	13	0
interop-pydantic-ai	9	0
retrievechat-pgvector	10	0
twilio	9	0
interop-langchain	9	0
graph-rag-falkor-db	6	0
docs	6	0
crawl4ai	13	0
interop-crewai	9	0
lmm	4	0
teachable	4	0
cerebras	15	1
agent-eval	1	0
gpt-assistant-agent	3	0
llama-index-agent	3	0
together	14	0
swarm	14	0
cohere	15	0
ollama	15	1
retrievechat-couchbase	3	0
mistral	14	0
anthropic	16	1
bedrock	15	1
gemini	14	1
websurfer	15	0
long-context	3	0
groq	14	0
integration	12	0
falkordb	2	0
autobuild	1	0
neo4j	2	0

see 36 files with indirect coverage changes

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