Bump download-artifact action to v3 (#447)

v2 is being deprecated

.github/workflows/build.yml

@@ -60,7 +60,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: Download compiled launcher
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v3
         with:
           name: northstar-launcher
           path: northstar-launcher
@@ -171,7 +171,7 @@ jobs:
 
       - name: Download Northstar package
         if: ${{ !env.ACT }} # Download artifacts from previous jobs when running on GitHub's infrastructure
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v3
         with:
           name: Northstar.release.${{ env.NORTHSTAR_VERSION }}
           path: northstar