chore(ci): bump actions/download-artifact from 6 to 8 (#1347)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 6 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v6...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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/deploy-demo.yml

@@ -137,7 +137,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Download frontend artifact
-        uses: actions/download-artifact@v6
+        uses: actions/download-artifact@v8
         with:
           name: frontend-dist
           path: frontend-dist/

.github/workflows/e2e.yml

@@ -110,7 +110,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Download backend binary
-        uses: actions/download-artifact@v6
+        uses: actions/download-artifact@v8
         with:
           name: meridian-binary
           path: dist/
@@ -119,7 +119,7 @@ jobs:
         run: chmod +x dist/meridian dist/seed-dev
 
       - name: Download frontend build
-        uses: actions/download-artifact@v6
+        uses: actions/download-artifact@v8
         with:
           name: frontend-dist
           path: frontend/dist/
@@ -251,7 +251,7 @@ jobs:
         run: npm ci
 
       - name: Download blob reports
-        uses: actions/download-artifact@v6
+        uses: actions/download-artifact@v8
         with:
           pattern: blob-report-*
           path: frontend/all-blob-reports

.github/workflows/test.yml

@@ -125,7 +125,7 @@ jobs:
         run: go mod download
 
       - name: Download coverage artifacts
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
         with:
           pattern: coverage-shard-*
           path: coverage-shards