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](actions/download-artifact@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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci_common.yml

@@ -266,7 +266,7 @@ jobs:
           echo "VERSION_MAJOR=${VERSION_MAJOR}"
 
       - name: Download release VSIX
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: azdo-task
           path: output
@@ -364,12 +364,12 @@ jobs:
           echo "VERSION_SHORT: $VERSION_SHORT"
 
       - name: Download workflow artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: output
 
       - name: Download release VSIX
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: azdo-task-dev
           path: output