Update CONTRIBUTING.md

Co-authored-by: Artem Pelenitsyn <[email protected]>

Author: TeofilC

CONTRIBUTING.md

@@ -343,7 +343,7 @@ Preview Releases
 We make preview releases available to facilitate testing of development builds.
 
 Artifacts can be found on the [`cabal-head` release page](https://github.com/haskell/cabal/releases/tag/cabal-head).
-Each CI pipeline generates tarballs with a `cabal` executable, and pipelines on `HEAD` also update this release.
+The Validate CI pipeline generates tarballs with a `cabal` executable. The executable gets uploaded to this release by the pipelines that run on `master`.
 
 We currently make available builds for:
   - Linux, dynamically linked (requiring `zlib`, `gmp`, `glibc`)