Update JetBrains.Annotations 2020.3.0 -> 2021.2.0
Update JetBrains.Annotations 2020.3.0 -> 2021.2.0

fluentassertions/fluentassertions,dennisdoomen/fluentassertions,dennisdoomen/fluentassertions,fluentassertions/fluentassertions,jnyrup/fluentassertions,jnyrup/fluentassertions