Fixing flaky distinct test

[coveralls]

Pull Request Test Coverage Report for Build 226

• 7 of 11 (63.64%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.05%) to 87.898%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/rx/objects/Observable.mon	0	1	0.0%
src/rx/operators/internals/Range.mon	7	10	70.0%
<!--	Total:	7	11	63.64%	-->

Totals
Change from base Build 222:	-0.05%
Covered Lines:	2057
Relevant Lines:	2329

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💛 - Coveralls