chore(deps): update dependency @types/node to v16 (#525)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [@types/node](https://togithub.com/DefinitelyTyped/DefinitelyTyped) | [`^14.0.0` -> `^16.0.0`](https://renovatebot.com/diffs/npm/@types%2fnode/14.17.32/16.11.6) | [![age](https://badges.renovateapi.com/packages/npm/@types%2fnode/16.11.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/npm/@types%2fnode/16.11.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/npm/@types%2fnode/16.11.6/compatibility-slim/14.17.32)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/npm/@types%2fnode/16.11.6/confidence-slim/14.17.32)](https://docs.renovatebot.com/merge-confidence/) |

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packages/google-cloud-iot/package.json

@@ -47,7 +47,7 @@
   },
   "devDependencies": {
     "@types/mocha": "^8.0.0",
-    "@types/node": "^14.0.0",
+    "@types/node": "^16.0.0",
     "@types/sinon": "^10.0.0",
     "c8": "^7.2.1",
     "gts": "^2.0.0",