Update CONTRIBUTING.md

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Merge pull request #173 from EricpolUkraine/development

Release v1.11.1
Removed unit test with probabilistic outcome. It can fail with low probability was needed to test if two same messages in a row appear at statistically calculated rate
Merge remote-tracking branch 'upstream/master' into development
Merge pull request #174 from Bohdan-Tereta/development

Unit test with probabilistic outcome removed