fix(deps): update rust crate async-openai to 0.21.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
async-openai	dependencies	minor	0.20.0 -> 0.21.0

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Release Notes

64bit/async-openai (async-openai)

### [`v0.21.0`](https://togithub.com/64bit/async-openai/releases/tag/async-openai-v0.21.0): v0.21.0 [Compare Source](https://togithub.com/64bit/async-openai/compare/async-openai-v0.20.0...async-openai-v0.21.0) ##### New **Added** - Batch API - Vector Stores API - Support for OpenAI Project ID - List checkpoints Fine Tuning API - Delete messages API **Updated** - Types for Assistant API v2 - Types for Audio translations API - Type `ApiError` to match spec. - Doc comments from spec.

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Configuration

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