Update build.yml

Fix build warning

Author: mooflu

.github/workflows/build.yml

@@ -64,7 +64,7 @@ jobs:
         run: tar -C ./build -cvf webapp.tar .
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v3
         with:
           name: webapp
           path: webapp.tar