Install PL dev intead of PL stable on CI #1509

	name: Formatting check
	on:
	- pull_request

	jobs:
	black:
	runs-on: ubuntu-latest
	steps:
	- name: Cancel Previous Runs
	uses: styfle/[email protected]
	with:
	access_token: ${{ github.token }}

	- name: Set up Python
	uses: actions/setup-python@v2
	with:
	python-version: 3.9

	- name: Install dependencies
	run: pip install black

	- uses: actions/checkout@v2

	- name: Run Black
	run: black -l 100 pennylane_qiskit/ --check

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