Bump actions/download-artifact from 5 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/release.yaml

@@ -62,7 +62,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Download artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           pattern: artifacts-*
           merge-multiple: true

.github/workflows/validate.yml

@@ -436,7 +436,7 @@ jobs:
           cabal-version: latest # default, we are not using it in this job
 
       - name: Download cabal executable from workflow artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: cabal-${{ runner.os }}-${{ env.CABAL_ARCH }}
           path: cabal-head
@@ -460,7 +460,7 @@ jobs:
     needs: [validate, validate-old-ghcs, build-alpine, dogfooding]
 
     steps:
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         with:
           pattern: cabal-*
           path: binaries
@@ -488,7 +488,7 @@ jobs:
     needs: [validate, validate-old-ghcs, build-alpine, dogfooding]
 
     steps:
-    - uses: actions/download-artifact@v5
+    - uses: actions/download-artifact@v6
       with:
         pattern: cabal-*
         path: binaries