[CHORE] Remove deprecated GitHub Learning Lab reference in README.md

[yashsinghal1234]

Description

GitHub officially retired and shut down the GitHub Learning Lab (https://lab.github.com/) in 2022. Our main README.md file still contains a reference to this deprecated resource.

Since GitHub Skills is the modern replacement, and we already have a similar resource section, we should remove this deprecated link to keep the README current and free of broken links.

Location of the Issue

• File: README.md (Line 291)
• Code snippet:

  - [GitHub Learning Lab](https://lab.github.com/)

(Note to Maintainers: Please label this as level 1 and NSoC'26)

[yashsinghal1234]

I would like to be assigned to this

[yashsinghal1234]

Please label this as level 1 and NSoC'26