[Bug]: GeminiClient fails when registering a function with Annotated type

[rjambrecic]

Describe the bug

Gemini isn't working when there is agent with tool parameter like this:

additional_notes: Annotated[Optional[str], "Additional notes"] = None

Here is a test case which is failing:

@pytest.mark.gemini
def test_gemini_with_tools_parameters_set_to_is_annotated_with_none_as_default_value(
    credentials_gemini_pro: Credentials,
) -> None:
    agent = ConversableAgent(name="agent", llm_config=credentials_gemini_pro.llm_config)

    user_proxy = UserProxyAgent(
        name="user_proxy_1",
        human_input_mode="NEVER",
    )

    mock = MagicMock()

    @user_proxy.register_for_execution()
    @agent.register_for_llm(description="Login function")
    def login(
        additional_notes: Annotated[Optional[str], "Additional notes"] = None,
    ) -> str:
        return "Login successful."

    user_proxy.initiate_chat(agent, message="Please login", max_turns=2)

    mock.assert_called_once()

This test is already in the test/agentchat/test_conversable_agent.py but currently it is marked with @pytest.skip because it is failing

Steps to reproduce

No response

Model Used

No response

Expected Behavior

No response

Screenshots and logs

No response

Additional Information

No response