chore(deps): bump Python version to 3.11.9

What does this merge request do and why?

This MR bumps Python version from 3.10.14 to 3.11.9.

https://docs.python.org/3.11/whatsnew/3.11.html

Python 3.11 is up to 10-60% faster than Python 3.10

How to set up and validate locally

1. Check out to this merge request's branch.

2. Ensure a local Docker image built successfully.

   docker build --platform linux/amd64 -t ai-gateway:dev .

3. Run a local service on Docker to confirm the it boots correctly.

   docker run -it --platform linux/amd64 --rm -p 5052:5000 \
       -e AIGW_AUTH__BYPASS_EXTERNAL=true \
       -e AIGW_USE_FAKE_MODELS=false \
       -e AIGW_GITLAB_URL="http://gdk.test:8080/" \
       -e AIGW_GITLAB_API_URL="http://gdk.test:8080/api/v4/" \
       -e AIGW_CUSTOMER_PORTAL_BASE_URL=https://customers.staging.gitlab.com \
       -e ANTHROPIC_API_KEY=$ANTHROPIC_TOKEN \
       ai-gateway:dev

4. In another terminal window, run a test cURL command and confirm 200 response.

   curl --request POST \
     --url http://ai-gateway.gdk.test:5052/v1/chat/agent \
     --header 'Content-Type: application/json' \
     --header 'X-Gitlab-Authentication-Type: oidc' \
     --header "authorization: Bearer $ANTHROPIC_TOKEN" \
     --data '{
     "prompt_components": [
       {
         "type": "prompt",
         "metadata": {
           "source": "test-source",
           "version": "no-version"
         },
         "payload": {
           "content": [
             {
               "role": "system",
               "content": "You are a Python engineer"
             },
             {
               "role": "user",
               "content": "define a function that adds numbers together"
             }
           ],
           "provider": "anthropic",
           "model": "claude-3-sonnet-20240229",
           "params": {
             "stop_sequences": [
               "\n\nHuman",
               "Observation:"
             ],
             "temperature": 0.1
           }
         }
       }
     ]
   }'

Merge request checklist

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