Regression when using Roslyn 3.7 in tests

[JohanLarsson]

Broke a couple of tests, changing back to 3.3.1 for now
https://dev.azure.com/DotNetAnalyzers/PropertyChangedAnalyzers/_build/results?buildId=1648&view=ms.vss-test-web.build-test-results-tab&runId=4166&resultId=101186&paneView=debug