fix: max completion tokens error

[roerohan]

What does this PR do?

Passes the max_completion_tokens parameter instead of max_tokens parameter in Cloudflare AI Gateway.

How did you verify your code works?

Before:

After:

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on the search results, here are the potentially related PRs:

1. PR #6534: Handle Cloudflare AI Gateway responses for codex models

   • Directly related to Cloudflare AI Gateway handling - may already address similar parameter issues

2. PR #5541: fix: use max_completion_tokens for Azure reasoning models

   • Addresses the same max_completion_tokens vs max_tokens parameter issue but for Azure reasoning models - similar pattern of fix

3. PR #5036: Fix/cerebras conservative max tokens

   • Related to max tokens handling for another provider (Cerebras) - similar type of token limit fix

These PRs may have already addressed similar parameter mapping issues for different providers. You should check if PR #6534 in particular already handles Cloudflare AI Gateway parameters, as it seems directly relevant.