Update Actions to v6 (major) #256

Job	Run time
lint-unit / runner / RSpec ubuntu-latest	36s
lint-unit / runner / linkspector	44s
lint-unit / runner / Check Metadata	7s
lint-unit / runner / Cookstyle	26s
lint-unit / runner / markdownlint	4s
lint-unit / runner / yamllint	12s
integration-windows	0s
integration	0s
integration-macos	0s
	2m 9s

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