Add specs for `for` loop with attribute target #1652

Job	Run time
RuboCop	24s
specs (ubuntu, 3.0.6)	1m 32s
specs (ubuntu, 3.1.4)	1m 30s
specs (ubuntu, 3.2.2)	1m 23s
specs (ubuntu, 3.3.0)	1m 22s
specs (macos, 3.0.6)	1m 20s
specs (macos, 3.1.4)	1m 22s
specs (macos, 3.2.2)	1m 22s
specs (macos, 3.3.0)	1m 10s
specs (windows, 3.0.6)	3m 28s
specs (windows, 3.1.4)	5m 9s
specs (windows, 3.2.2)	4m 58s
specs (windows, 3.3.0)	5m 1s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 23s
	31m 24s

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