CI stack: cabal sdist source is the right command

.github/workflows/stack.yml

@@ -114,12 +114,8 @@ jobs:
           startsWith(github.ref, 'refs/tags/v')
           && matrix.ghc == '9.0.1'
         run: |
-          cabal sdist
-          export DIST_TGZ=$(cabal sdist | tail -1)
+          export DIST_TGZ=$(cabal sdist source | tail -1)
           echo "DIST_TGZ=${DIST_TGZ}" >> ${GITHUB_ENV}
-        # Note: we do sdist twice because the first time it might print stuff like
-        # "Writing default configuration to /home/runner/.cabal/config"
-        # that spoils our `tail -1` hack.
 
       - name: Source tarball release.
         if: >-