chore(deps): bump actions/download-artifact from 4 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...v8)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/nightly.yml

@@ -429,7 +429,7 @@ jobs:
       - image-build-arm
     steps:
       - name: Download digests
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           path: ${{ runner.temp }}/digests
           pattern: digests-*
@@ -468,7 +468,7 @@ jobs:
       - image-build-arm-distroless
     steps:
       - name: Download digests
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           path: ${{ runner.temp }}/digests
           pattern: digests-distroless-*
@@ -506,7 +506,7 @@ jobs:
       - binary-build
       - binary-build-arm
     steps:
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           pattern: tinyauth-*
           path: binaries