ci: github: bump dawidd6/action-download-artifact from 3 to 6

Bumps [dawidd6/action-download-artifact](https://github.com/dawidd6/action-download-artifact) from 3 to 6.
- [Release notes](https://github.com/dawidd6/action-download-artifact/releases)
- [Commits](https://github.com/dawidd6/action-download-artifact/compare/v3...v6)

---
updated-dependencies:
- dependency-name: dawidd6/action-download-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

.github/workflows/bsim-tests-publish.yaml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Download artifacts
-        uses: dawidd6/action-download-artifact@v3
+        uses: dawidd6/action-download-artifact@v6
         with:
           run_id: ${{ github.event.workflow_run.id }}
 

.github/workflows/doc-publish-pr.yml

@@ -21,7 +21,7 @@ jobs:
 
     steps:
     - name: Download artifacts
-      uses: dawidd6/action-download-artifact@v3
+      uses: dawidd6/action-download-artifact@v6
       with:
         workflow: doc-build.yml
         run_id: ${{ github.event.workflow_run.id }}

.github/workflows/doc-publish.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
     - name: Download artifacts
-      uses: dawidd6/action-download-artifact@v3
+      uses: dawidd6/action-download-artifact@v6
       with:
         workflow: doc-build.yml
         run_id: ${{ github.event.workflow_run.id }}