Fix embedded pdf path to github-account-security.mdx

[inaambaj]

Please check the following - and then delete this message:

• If you are creating a new page, does it contain the following value at the top, with x being the position in the folder?

---
sidebar_position: x
---

• If you are creating a new sub-folder, does it have a _category_.json file with the appropriate descriptive information?
• Are all your images / videos named appropriately and in the correct location ("image1.png" e.g. will not be accepted)
• Are all your code blocks properly closed off?
• Does your file have an appropriate and descriptive file name, and main header?
• Ensure all files are referenced correctly (They are case sensitive - if you save "image.png" you cannot reference "Image.PNG")

Failure to include these will result in your request not being reviewed.

[VishalAbiman05]

Security review – PR #328

This change replaces an absolute URL with a relative path for a PDF embed.
This is good practice because it avoids external dependencies and reduces the risk of content injection or MITM attacks if the external domain were compromised.

No security issues found.

[Mouse933]

Already reviewed by Vishal, no issues found. Approving to push to main :)