Document Qwen model for Code Suggestions removal in GitLab 17.11

What does this MR do and why?

What? Add a link to the removal that happened in Resolve "Remove Fireworks/Qwen support for SaaS" (!187397 - merged). Why? Help spread knowledge of possible impact of removing this model from the GitLab-hosted AI gateway which could still be access by GitLab 17.10 and earlier for self-managed users.

References

• Resolve "Remove Fireworks/Qwen support for SaaS" (!187397 - merged)

• Question that inspired this docs update in Slack:

  Hello, is the qwen2p5-coder-7b model still used to power code completions?

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Before	After

How to set up and validate locally

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