chore(deps): update @slack/bolt requirement from ^4.2.0 to ^4.2.1 in /examples/deploy-heroku (#2477)

Author: dependabot[bot]

examples/deploy-heroku/package.json

@@ -9,6 +9,6 @@
   },
   "license": "MIT",
   "dependencies": {
-    "@slack/bolt": "^4.2.0"
+    "@slack/bolt": "^4.2.1"
   }
 }