docs: fix broken link in auth dependencies guide

Fix MkDocs build error by removing markdown link to source code file.
Change from [API Dependencies](../app/api/deps.py) to plain text
reference to avoid strict mode warning about non-documentation files.

Fixes: Doc file contains a link to 'app/api/deps.py' not in docs

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Co-Authored-By: Claude <noreply@anthropic.com>

docs/development/AUTH_DEPENDENCIES_GUIDE.md

@@ -188,4 +188,4 @@ from app.api.deps import get_current_user  # Header-only, any role
 
 - [Authentication Documentation](../api/authentication.md) - Complete auth system docs
 - [Authentication Flow Diagrams](../api/authentication-flow-diagrams.md) - Visual flows
-- [API Dependencies](../app/api/deps.py) - Source code
+- Source code: `app/api/deps.py` - Authentication dependency implementations