fix(openai): correct `reasoning_effort_levels` for gpt-5 and gpt-5.1 profiles (#39936)

Fixes #39935

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`gpt-5`, `gpt-5-mini`, `gpt-5-nano` and `gpt-5.1` no longer advertise a
reasoning effort level they reject, and the GPT-5 models advertise
`minimal` again.

The profile augmentations currently give all four models `["none",
"low", "medium", "high", "xhigh"]`. OpenAI's [GPT-5 model
page](https://developers.openai.com/api/docs/models/gpt-5) states that
effort supports "minimal, low, medium, and high", and the [GPT-5.1
page](https://developers.openai.com/api/docs/models/gpt-5.1) lists "none
(default), low, medium, and high". `xhigh` arrived later, with
GPT-5.1-Codex-Max.

A client that reads `profile["reasoning_effort_levels"]` to build its
settings therefore offers `xhigh` on models that reject it, and hides
`minimal`, which GPT-5 accepts. The corrected values match the
models.dev entries for the same models.

The `gpt-5.2` / `gpt-5.4` / `gpt-5.6` profiles are already correct and
are untouched. A few other entries (`gpt-5-pro`, `gpt-5.2-pro`,
`gpt-5.4-pro`, `gpt-5.2-chat-latest`) also differ from models.dev, but I
could not confirm those from OpenAI's own docs, so I left them alone.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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Co-authored-by: Mason Daugherty <mason@langchain.dev>