fix: example/postgres/package.json to reduce vulnerabilities (#275)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-SEMVER-3247795

Co-authored-by: snyk-bot <[email protected]>

Author: decompil3d

example/postgres/package.json

@@ -9,6 +9,6 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "pg": "^7.18.2"
+    "pg": "^8.4.0"
   }
 }