Fix AI Gateway URL

What does this MR do and why?

!138914 (merged) added new API endpoint proxying to AI Gateway. However AI Gateway endpoint path had typo in it. This MR fixes typo

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Before	After

How to set up and validate locally

1. Make sure that AI Gateway is working on your local env
2. Select Ci::Build from namespace with code suggestions add on purchased
3. Update build state to running
4. Set build token to any value eg: secret

project = Project.find 2
build = project.builds.first
build.set_token 'secret'
build.status = "running"
build.save
namespace = build.project.namespace
FactoryBot.create(:gitlab_subscription_add_on_purchase, add_on: FactoryBot.create(:gitlab_subscription_add_on), namespace: namespace)

Use build id and token to make curl request to API endpoint

 curl -v -X POST -H "Content-Type: Application/json"  http://gdk.test:3000/api/v4/internal/jobs/1/x_ray/scan --data '{
  "token": "tajnyToken",
  "prompt_components": [
     {
       "type":"x_ray_package_file_prompt",
       "payload":{
         "prompt": "Human: Parse following content of {file_name}. Respond using only valid JSON with list of libraries available to use and their short description\n\n{file_name} content:\n\n```\n{content}\n```\n\n Assistant: {{\n\"libraries\":[{{\"name\": \"",
         "provider": "anthropic",
         "model": "claude-2.0"
       },
       "metadata": { "scannerVersion": "0.0.1" }
     }
  ]
 }'

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