Fix some typos in help messages and command doco #1031

Job	Run time
test (ubuntu-latest, 26.3, false)	1m 3s
test (ubuntu-latest, 27.2, false)	1m 4s
test (ubuntu-latest, 28.2, false)	59s
test (ubuntu-latest, 29.4, false)	1m 12s
test (macos-latest, 28.2, false)	1m 59s
test (macos-latest, 29.4, false)	2m 24s
test (windows-latest, 26.3, false)	3m 27s
test (windows-latest, 27.2, false)	1m 57s
test (windows-latest, 28.2, false)	2m 28s
test (windows-latest, 29.4, false)	2m 9s
test (ubuntu-latest, snapshot, true)	54s
test (macos-latest, snapshot, true)	1m 37s
test (windows-latest, snapshot, true)	3m 38s
	24m 51s

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