docs: update CONTRIBUTING.md (#1270)

Author: rquadling

CONTRIBUTING.md

@@ -186,7 +186,6 @@ docker buildx bake -f docker-bake.hcl --pull --no-cache --push
 * [PHP embedding in C++](https://gist.github.com/paresy/3cbd4c6a469511ac7479aa0e7c42fea7)
 * [Extending and Embedding PHP by Sara Golemon](https://books.google.fr/books?id=zMbGvK17_tYC&pg=PA254&lpg=PA254#v=onepage&q&f=false)
 * [What the heck is TSRMLS_CC, anyway?](http://blog.golemon.com/2006/06/what-heck-is-tsrmlscc-anyway.html)
-* [PHP embedding on Mac](https://gist.github.com/jonnywang/61427ffc0e8dde74fff40f479d147db4)
 * [SDL bindings](https://pkg.go.dev/github.com/veandco/go-sdl2@v0.4.21/sdl#Main)
 
 ## Docker-Related Resources