buildah: don't modify Dockerfile in place #1462

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Status	Duration	Name
✅ Succeeded	20 seconds	fetch-repository
✅ Succeeded	19 seconds	check-task-migration-md
✅ Succeeded	21 seconds	task-lint-check
✅ Succeeded	24 seconds	sast-snyk-check
✅ Succeeded	41 seconds	ec-task-checks
✅ Succeeded	2 minutes	build-container
✅ Succeeded	19 seconds	check-partner-tasks
✅ Succeeded	1 minute	build-bundles
✅ Succeeded	16 minutes	e2e-tests
✅ Succeeded	1 minute	check-task-pipeline-repo-existence
✅ Succeeded	7 seconds	e2e-cleanup