Fix some typos in help messages and command doco (#280) #1032

Job	Run time
test (ubuntu-latest, 26.3, false)	52s
test (ubuntu-latest, 27.2, false)	56s
test (ubuntu-latest, 28.2, false)	1m 3s
test (ubuntu-latest, 29.4, false)	1m 26s
test (macos-latest, 28.2, false)	1m 46s
test (macos-latest, 29.4, false)	2m 7s
test (windows-latest, 26.3, false)	5m 17s
test (windows-latest, 27.2, false)	2m 33s
test (windows-latest, 28.2, false)	1m 48s
test (windows-latest, 29.4, false)	3m 35s
test (ubuntu-latest, snapshot, true)	51s
test (macos-latest, snapshot, true)	1m 38s
test (windows-latest, snapshot, true)	3m 13s
	27m 5s

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