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] <[email protected]>

Author: dependabot[bot]

.github/workflows/docsite.yml

@@ -30,7 +30,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v5
       - name: Download artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: site
           path: site

.github/workflows/release-asset.yml

@@ -89,7 +89,7 @@ jobs:
           fetch-depth: 0  # Needed for changelog generation
 
       - name: Download build artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: elixir-ls-${{ needs.build.outputs.version }}
 
@@ -133,7 +133,7 @@ jobs:
     needs: build
     steps:
       - name: Download build artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: elixir-ls-${{ needs.build.outputs.version }}