Docker - use more convenient value for the `client_max_body_size` directive

[osokin]

Describe the bug

The client_max_body_size 0; is potentially dangerous; increase it to a more convenient value.

To reproduce

Steps to reproduce the behavior:

1. Open https://docs.nginx.com/waf/install/docker/#multi-container-configuration
2. View output
3. See error

Expected behavior

A clear and concise description of what you expected to happen.

Your environment

macOS/Chrome

Additional context

No any other context about the problem here.

Sensitive Information

No any sensitive information such as authentication credentials or license keys.

[ADubhlaoich]

Blocked, waiting for guidance from internal SMEs.