drop node 16 from ci #257

# to view logs

Job	Run time
build (18.x, ubuntu-latest, bash)	48s
build (18.x, macos-latest, bash)	1m 18s
build (18.x, windows-latest, bash)	1m 27s
build (18.x, windows-latest, powershell)	1m 17s
build (20.x, ubuntu-latest, bash)	40s
build (20.x, macos-latest, bash)	1m 23s
build (20.x, windows-latest, bash)	1m 26s
build (20.x, windows-latest, powershell)	1m 27s
build (21.x, ubuntu-latest, bash)	44s
build (21.x, macos-latest, bash)	1m 21s
build (21.x, windows-latest, bash)	1m 10s
build (21.x, windows-latest, powershell)	1m 21s
	14m 22s

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