chore(deps): update dependency @types/node to v20 (#1846)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [@types/node](https://togithub.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/node) ([source](https://togithub.com/DefinitelyTyped/DefinitelyTyped)) | [`^18.0.0` -> `^20.0.0`](https://renovatebot.com/diffs/npm/@types%2fnode/18.18.6/20.8.8) | [![age](https://developer.mend.io/api/mc/badges/age/npm/@types%2fnode/20.8.8?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/@types%2fnode/20.8.8?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/@types%2fnode/18.18.6/20.8.8?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/@types%2fnode/18.18.6/20.8.8?slim=true)](https://docs.renovatebot.com/merge-confidence/) |

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package.json

@@ -73,7 +73,7 @@
     "@types/mocha": "^9.0.0",
     "@types/mv": "^2.1.0",
     "@types/ncp": "^2.0.1",
-    "@types/node": "^18.0.0",
+    "@types/node": "^20.0.0",
     "@types/proxyquire": "^1.3.28",
     "@types/sinon": "^10.0.0",
     "@types/tmp": "^0.2.0",

system-test/fixtures/sample/package.json

@@ -16,7 +16,7 @@
     "@google-cloud/pubsub": "file:./pubsub.tgz"
   },
   "devDependencies": {
-    "@types/node": "^18.0.0",
+    "@types/node": "^20.0.0",
     "typescript": "^4.6.4",
     "gts": "^3.1.0"
   }