Update Actions to v6 (major) #263

Job	Run time
lint-unit / runner / markdownlint	6s
lint-unit / runner / Check Metadata	7s
lint-unit / runner / actionlint	10s
lint-unit / runner / linkspector	44s
lint-unit / runner / yamllint	8s
lint-unit / runner / RSpec ubuntu-latest	38s
lint-unit / runner / Cookstyle	14s
integration	-1s
integration-windows	-1s
integration-macos	-1s
	2m 4s

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