Upgrade to minintest 6 #16301

Job	Run time
lint_ruby	29s
Verify Jekyll website builds	11s
spelling	16s
lint_node	37s
build_node (macos-latest)	3m 32s
build_node (ubuntu-latest)	2m 33s
build_node (windows-latest)	6m 47s
Ruby 4.0 on ubuntu-latest	11m 30s
Ruby 3.4 on ubuntu-latest	12m 4s
Ruby 3.3 on ubuntu-latest	12m 39s
Ruby 4.0 on macos-latest	7m 21s
Ruby 3.3 on macos-latest	6m 49s
Ruby 3.3 on windows-latest	28m 20s
Ruby 3.4 on macos-latest	9m 13s
Ruby 3.4 on windows-latest	27m 23s
Ruby 4.0 on windows-latest	28m 1s
	2h 37m 45s

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