Merge pull request #7121 from DanHam/contributing-link

Fix a link in the contributing doc

.github/CONTRIBUTING.md

@@ -107,7 +107,9 @@ From there, open your fork in your browser to open a new pull-request.
 will break if you `git clone` your fork instead of using `go get` on the main
 Packer project.
 
-**Note:** See [Working on forks](#Working on forks) for a better way to use `git push ...`.
+**Note:** See '[Working with
+forks](https://help.github.com/articles/working-with-forks/)' for a better way
+to use `git push ...`.
 
 ### Pull Request Lifecycle