Disable $RUBYOPT env variable in specs that expects there are no --en… #1590

Job	Run time
RuboCop	23s
specs (ubuntu, 3.0.6)	1m 28s
specs (ubuntu, 3.1.4)	1m 32s
specs (ubuntu, 3.2.2)	1m 23s
specs (ubuntu, 3.3.0)	1m 22s
specs (macos, 3.0.6)	1m 49s
specs (macos, 3.1.4)	1m 37s
specs (macos, 3.2.2)	1m 43s
specs (macos, 3.3.0)	1m 37s
specs (windows, 3.0.6)	4m 8s
specs (windows, 3.1.4)	4m 3s
specs (windows, 3.2.2)	4m 55s
specs (windows, 3.3.0)	3m 58s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 21s
	31m 19s

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