LiteLLM Gemini 3 provider always injects temperature=1.0 even when caller omits it; additional_drop_params cannot remove it

Finding: According to an external report on BerriAI/litellm issue #45333 (no KFA reproduction), for Gemini 3 or newer models the Vertex/Gemini config in map_openai_params adds temperature=1.0 whenever the caller did not set a temperature, and additional_drop_params=["temperature"] does not remove it. The reporter says this reproduces on 1.82.0, 1.104.0, 1.104.2, 1.105.0rc3 and 1.106.0.dev2 (https://github.com/BerriAI/litellm/issues/45333). Reported evidence: the reporter's snippet calls get_optional_params with model gemini-3.1-pro-preview, custom_llm_provider gemini and reasoning_effort high. The result contains thinkingConfig plus temperature 1.0. Adding additional_drop_params for temperature gives the same output. The reporter attributes this to the default being applied after the drop filter, based on reading the code near line 1230 of the 1.104.2 source. This is the reporter's analysis; no maintainer confirmed it in the supplied comments. Why it may matter: the reporter says Google is notifying projects that upcoming Gemini models will return an error when temperature, top_p or top_k is sent, and that thinking_budget will return 400 INVALID_ARGUMENT. This notice is second-hand and was not verified against Google documentation or a live endpoint here. If it is accurate, callers could not avoid sending temperature through LiteLLM's Gemini 3 path. Fix status: a commenter says PR #45387 removes the forced default and adds regression coverage (https://github.com/BerriAI/litellm/issues/45333#issuecomment-6063883541). The PR itself was not supplied, so its contents, review state, merge and release are unknown. No released fix is established. Workaround: none is supported by the supplied sources. The reporter states omitting temperature and using additional_drop_params do not help. Limitations: single external report, no maintainer response, not tested against a live Gemini endpoint, and comments coverage may omit middle comments. Treat the affected-version list as reported, not verified.