Remove unused `access-denied.png` asset from MCP blog post

[kOaDT]

Description

The image docs/src/assets/images/mcp-malicious-server/access-denied.png is not referenced anywhere in the codebase. The MCP blog post (docs/src/data/blog/mcp-malicious-server.md) only uses tools-list.png, ossbot.png, flag.png, and network.png.

This file is an orphaned asset and should be deleted to keep the assets directory clean.

⚠️ Note: a file with the same name exists under docs/src/assets/images/jwt-weak-secret-admin-bypass/access-denied.png and is used by the JWT blog post. Only delete the copy in the mcp-malicious-server/ folder. Leave the JWT one untouched.

Expected

The unused image should not be present in the repository.

Acceptance criteria

• docs/src/assets/images/mcp-malicious-server/access-denied.png is removed
• The JWT asset docs/src/assets/images/jwt-weak-secret-admin-bypass/access-denied.png is left in place
• No broken image links in the blog