chore(deps): Bump pg and @types/pg in /examples/node-pg

Bumps [pg](https://github.com/brianc/node-postgres/tree/HEAD/packages/pg) and [@types/pg](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/pg). These dependencies needed to be updated together.

Updates `pg` from 8.11.3 to 8.20.0
- [Changelog](https://github.com/brianc/node-postgres/blob/master/CHANGELOG.md)
- [Commits](https://github.com/brianc/node-postgres/commits/pg@8.20.0/packages/pg)

Updates `@types/pg` from 8.10.9 to 8.20.0
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/pg)

---
updated-dependencies:
- dependency-name: pg
  dependency-version: 8.20.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: "@types/pg"
  dependency-version: 8.20.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]