Revert "This spec actually depends on fchdir being available" #1957

Job	Run time
specs (ubuntu, 3.1.6)	1m 34s
RuboCop	49s
specs (ubuntu, 3.2.7)	1m 29s
specs (ubuntu, 3.3.7)	1m 24s
specs (ubuntu, 3.4.2)	1m 33s
specs (macos, 3.1.6)	1m 19s
specs (macos, 3.2.7)	1m 7s
specs (macos, 3.3.7)	1m 8s
specs (macos, 3.4.2)	1m 11s
specs (windows, 3.1.6)	5m 13s
specs (windows, 3.2.7)	5m 14s
specs (windows, 3.3.7)	3m 45s
specs (windows, 3.4.2)	3m 49s
specs (ubuntu, 3.4.2, --enable-frozen-string-literal)	1m 36s
	31m 11s

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