Rewrap to match the rest

Author: tgross35

CONTRIBUTING.md

@@ -168,4 +168,9 @@ cargo bench --no-default-features \
 
 ## Subtree synchronization
 
-`compiler-builtins` is included as a [Josh subtree](https://rustc-dev-guide.rust-lang.org/external-repos.html#josh-subtrees) in the main compiler repository (`rust-lang/rust`). You can find a guide on how to create synchronization (pull and push) PRs [here](https://rustc-dev-guide.rust-lang.org/external-repos.html#synchronizing-a-josh-subtree).
+`compiler-builtins` is included as a [Josh subtree] in the main compiler
+repository (`rust-lang/rust`). You can find a guide on how to create synchronization
+(pull and push) PRs at the [`rustc-dev-guide` page].
+
+[Josh subtree]: https://rustc-dev-guide.rust-lang.org/external-repos.html#josh-subtrees
+[`rustc-dev-guide` page]: https://rustc-dev-guide.rust-lang.org/external-repos.html#synchronizing-a-josh-subtree