[docs] fix link to "Parallel Algorithm for Decision Tree" paper

[PriyadarshiAkshay]

The current hyperlink for Meng et al. 2016 redirects to a different proceeding at NeurIPS. Updated the link.

[StrikerRUS]

LGTM, thanks!

[StrikerRUS]

/AzurePipelines run

[jameslamb]

Thanks!

There was one more place using that same link, which I found like this:

git grep -i 'Communication-Efficient'

I've pushed a commit updating that.

Also... in the future, when you contribute to open source projects on GitHub, don't use the master / main branch of your fork. Create a new branch with your changes. As soon as this is merged, or it any other PRs are merged, master in this repo will have a different history than master on your fork, which will make future contributions difficult.

AFTER this PR is merged, you should delete and recreate your fork, to fix its master branch (if you plan to come back and contribute again... which we hope you do!).

For more information on this, see https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request

[StrikerRUS]

/AzurePipelines run

[PriyadarshiAkshay]

@microsoft-github-policy-service agree
@jameslamb thank you so much!