Change timeout to 60s

What does this merge request do and why?

This MR changes the timeout settings of Code Generation request for the AI Gateway Anthropic client from 30s to 60s

• Related to gitlab-org/gitlab!143855 (merged)
• For gitlab-org/gitlab#436430 (closed)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.