chore(deps): bump actions/download-artifact from 4 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...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>

.github/workflows/ghcr-build.yml

@@ -268,7 +268,7 @@ jobs:
         uses: docker/setup-buildx-action@v3
       - name: Download runtime source for fork
         if: github.event.pull_request.head.repo.fork
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: runtime-src-${{ matrix.base_image.tag }}
           path: containers/runtime
@@ -330,7 +330,7 @@ jobs:
         uses: docker/setup-buildx-action@v3
       - name: Download runtime source for fork
         if: github.event.pull_request.head.repo.fork
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: runtime-src-${{ matrix.base_image.tag }}
           path: containers/runtime

.github/workflows/py-tests.yml

@@ -113,7 +113,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - uses: actions/download-artifact@v5
+      - uses: actions/download-artifact@v6
         id: download
         with:
           pattern: coverage-*

.github/workflows/vscode-extension-build.yml

@@ -142,7 +142,7 @@ jobs:
 
     steps:
       - name: Download .vsix artifact
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: vscode-extension
           path: ./