fix(openai): add 'default' serviceTier to openaiResponsesProviderOptionsSchema

[DeJeune]

Background

OpenAI response/chat completion support default serviceTier Level

Related Links:
https://platform.openai.com/docs/api-reference/responses/create#responses-create-service_tier
https://platform.openai.com/docs/api-reference/chat/create#chat-create-service_tier

Checklist

• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added (for bug fixes / features - run pnpm changeset in the project root)
• Formatting issues have been fixed (run pnpm prettier-fix in the project root)
• I have reviewed this pull request (self-review)

[gr2m]

Thanks but already resolved by #9291 😅 sorry that we missed yours!