bump @actions/artifact to 2.0.0

package.json

@@ -29,7 +29,7 @@
   },
   "homepage": "https://github.com/actions/upload-artifact#readme",
   "dependencies": {
-    "@actions/artifact": "^1.1.1",
+    "@actions/artifact": "^2.0.0",
     "@actions/core": "^1.10.0",
     "@actions/glob": "^0.3.0",
     "@actions/io": "^1.1.2"