Update README.md (#1226)
* Update README.md
Based on https://developers.cloudflare.com/api/operations/workers-ai-post-run-cf-deepseek-ai-deepseek-math-7b-instruct#request-body, this is no longer accurate
* Remove warning in hosted docs too
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Co-authored-by: Nathan Sarrazin <sarrazin.nathan@gmail.com>
