Fix some typos in help messages and command doco #6

Job	Run time
test (ubuntu-latest, 26.3, false)	28s
test (ubuntu-latest, 27.2, false)	38s
test (ubuntu-latest, 28.2, false)	34s
test (ubuntu-latest, 29.4, false)	1m 48s
test (macos-latest, 28.2, false)	1m 9s
test (macos-latest, 29.4, false)	2m 4s
test (windows-latest, 26.3, false)	2m 29s
test (windows-latest, 27.2, false)	2m 26s
test (windows-latest, 28.2, false)	1m 8s
test (windows-latest, 29.4, false)	1m 28s
test (ubuntu-latest, snapshot, true)	29s
test (macos-latest, snapshot, true)	1m 28s
test (windows-latest, snapshot, true)	5m 4s
	21m 13s

Provide feedback