ci: Bump @actions/artifact from 1x to 2.x

This _should_ not break stuff for us: https://www.npmjs.com/package/@actions/artifact#v2---whats-new

Author: mydea

dev-packages/size-limit-gh-action/package.json

@@ -14,7 +14,7 @@
     "fix": "eslint . --format stylish --fix"
   },
   "dependencies": {
-    "@actions/artifact": "1.1.2",
+    "@actions/artifact": "2.1.9",
     "@actions/core": "1.10.1",
     "@actions/exec": "1.1.1",
     "@actions/github": "^5.0.0",