Remove SnakeYAML settings that don't work #21

Job	Run time
ruby-versions / Generate Ruby versions	2s
build (2.5, 0.1.7, /tmp/local)	58s
build (2.5, 0.1.7)	40s
build (2.5, 0.2.5, /tmp/local)	59s
build (2.5, 0.2.5)	33s
build (2.6, 0.1.7, /tmp/local)	55s
build (2.6, 0.1.7)	34s
build (2.6, 0.2.5, /tmp/local)	58s
build (2.6, 0.2.5)	37s
build (2.7, 0.1.7, /tmp/local)	57s
build (2.7, 0.1.7)	38s
build (2.7, 0.2.5, /tmp/local)	1m 7s
build (2.7, 0.2.5)	50s
build (3.0, 0.1.7, /tmp/local)	27s
build (3.0, 0.1.7)	19s
build (3.0, 0.2.5, /tmp/local)	34s
build (3.0, 0.2.5)	22s
build (3.1, 0.1.7, /tmp/local)	27s
build (3.1, 0.1.7)	21s
build (3.1, 0.2.5, /tmp/local)	34s
build (3.1, 0.2.5)	17s
build (3.2, 0.1.7, /tmp/local)	27s
build (3.2, 0.1.7)	17s
build (3.2, 0.2.5, /tmp/local)	28s
build (3.2, 0.2.5)	22s
build (head, 0.1.7, /tmp/local)	32s
build (head, 0.1.7)	17s
build (head, 0.2.5, /tmp/local)	29s
build (head, 0.2.5)	23s
	16m 24s

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