Update posts/inside-rust/2021-10-18-1.56.0-prerelease.md

Co-authored-by: Mark Rousskov <[email protected]>

Author: pietroalbini

posts/inside-rust/2021-10-18-1.56.0-prerelease.md

@@ -17,5 +17,5 @@ RUSTUP_DIST_SERVER=https://dev-static.rust-lang.org rustup update stable
 The index is <https://dev-static.rust-lang.org/dist/2021-10-18/index.html>. You
 can leave feedback on the [internals thread][internals].
 
-[relnotes]: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1560-2021-10-21
+[relnotes]: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1560-2021-10-21
 [internals]: https://internals.rust-lang.org/t/rust-1-56-0-pre-release-testing/15459