Update bundle config command, add instructions for PostgreSQL #1478

	---
	name: Automated tests
	on: pull_request
	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	ruby: ["3.0", "3.1", "3.2", "3.3"]
	db: [sqlite, mysql, postgres]
	exclude:
	- ruby: "3.1"
	db: sqlite
	- ruby: "3.1"
	db: postgres
	- ruby: "3.2"
	db: sqlite
	- ruby: "3.2"
	db: postgres

	steps:
	- uses: actions/checkout@v1
	- run: bash -x script/cibuild ${{ matrix.ruby }} ${{ matrix.db }}

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