add v1.31 regex, remove outdated versions from the list #33

	name: Lint Dockerfile
	on:
	pull_request:
	types: [opened, synchronize]

	jobs:
	lint:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- uses: hadolint/[email protected]
	with:
	failure-threshold: warning

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