docs: fix broken examples link (#86916)
### What?
Fix broken link in the documentation pointing to the examples folder.
### Why?
The previous link to the examples folder in
`docs/04-community/index.mdx` was incorrect:
https://github.com/vercel/next.js/tree/canary/contributing/examples
This caused confusion and 404 errors for contributors trying to access
the correct examples.
(the url page is in here
https://nextjs.org/docs/community/contribution-guide)
### How?
Updated the link in `docs/04-community/index.mdx` to point to the
correct folder:
from
https://github.com/vercel/next.js/tree/canary/contributing/examples
to
https://github.com/vercel/next.js/tree/canary/examples
Co-authored-by: Joseph <joseph.chamochumbi@vercel.com>
