docs: fix broken Erlang chat tutorial link

[chenlichao]

Description

Updates the Erlang "Making a Chat App with Erlang, Rebar, Cowboy and Bullet" entry to point to an archived copy of the original tutorial.

Motivation and Context

The current marianoguerra.org URL returns 404 Not Found. This fixes #840 by preserving the original tutorial through the Wayback Machine instead of leaving a broken link in the README.

How Has This Been Tested?

• git diff --check
• Verified the old URL returns HTTP Error 404: Not Found
• Verified the replacement archive URL returns 200 and contains the tutorial title

Types of changes

• Content Update (change which fixes an issue or updates an already existing submission)
• New Article (change which adds functionality)
• Documentation change

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have made checks to ensure URLs and other resources are valid

[tuvtran]

Thanks for the PR! The tutorial actually just moved to a new URL on the same site, so the entry now points at the live page (commit 9859dbe) instead of an archive snapshot. Appreciate the fix!