Bump actions/download-artifact from 7 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 7 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v7...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/docker_build.yml

@@ -113,7 +113,7 @@ jobs:
     steps:
       -
         name: Download digests
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           path: /tmp/digests
           pattern: digests-*

.github/workflows/docker_frankenphp.yml

@@ -114,7 +114,7 @@ jobs:
     steps:
       -
         name: Download digests
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           path: /tmp/digests
           pattern: digests-*