Update data-center-endpoints.md

[StuMinch]

Added an entry to call out permitting the wss:// endpoint for websocket communication. We're seeing an increase in support cases because CDP/BiDi requires wss to work, but customers have not permitted wss traffic within their environments.

Description

Motivation and Context

Types of Changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation fix (typos, incorrect content, missing content, etc.)