remove unnecessary skips #1083

Job	Run time
R-CMD-check / macOS-latest (release)	15m 7s
R-CMD-check / windows-latest (devel)	12m 42s
R-CMD-check / windows-latest (release)	12m 37s
R-CMD-check / windows-latest (oldrel)	12m 17s
R-CMD-check / ubuntu-latest (devel)	15m 9s
R-CMD-check / ubuntu-latest (release)	13m 38s
R-CMD-check / ubuntu-latest (oldrel)	10m 50s
R-CMD-check / ubuntu-latest (oldrel-2)	2m 42s
R-CMD-check / ubuntu-latest (oldrel-3)	6m 47s
R-CMD-check / ubuntu-latest (3.6)	3m 26s
	1h 45m 15s

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