Update some links

Author: JohnTitor

src/contributing.md

@@ -67,8 +67,8 @@ where contributors push changes to their personal fork and create pull requests
 bring those changes into the source repository. We have more info about how to use git
 when contributing to Rust under [the git section](./git.md).
 
-[about-pull-requests]: https://help.github.com/articles/about-pull-requests/
-[development-models]: https://help.github.com/articles/about-collaborative-development-models/
+[about-pull-requests]: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests
+[development-models]: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/getting-started/about-collaborative-development-models#fork-and-pull-model
 
 ### r?
 
@@ -177,7 +177,7 @@ particularly during rebasing, citing the issue number in the commit can "spam"
 the issue in question.
 
 [labeling]: ./rustbot.md#issue-relabeling
-[closing-keywords]: https://help.github.com/en/articles/closing-issues-using-keywords
+[closing-keywords]: https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue
 
 ### External Dependencies (subtree)
 

src/git.md

@@ -18,7 +18,7 @@ more in depth [book from Git].
 
 [book from Git]: https://git-scm.com/book/en/v2/
 [atlassian-git]: https://www.atlassian.com/git/tutorials/what-is-version-control
-[documentation]: https://docs.github.com/en/github/getting-started-with-github/set-up-git
+[documentation]: https://docs.github.com/en/get-started/quickstart/set-up-git
 [guides]: https://guides.github.com/introduction/git-handbook/
 
 ## Prerequisites

src/query.md

@@ -37,7 +37,7 @@ will in turn demand information about that crate, starting from the
   actual parsing.
 
 Although this vision is not fully realized, large sections of the
-compiler (for example, generating [MIR](./mir/)) currently work exactly like this.
+compiler (for example, generating [MIR](./mir/index.md)) currently work exactly like this.
 
 [^incr-comp-detail]: The ["Incremental Compilation in Detail](queries/incremental-compilation-in-detail.md) chapter gives a more
 in-depth description of what queries are and how they work.