Update analyzer versions (dotnet/corefx#40778)

In particular to pick up StyleCop fixes related to C# 8 and nullability.

Commit migrated from https://github.com/dotnet/corefx/commit/1bf90840626cd2e7b19377bd6a16b17de0e6e672

eng/Analyzers.props

 <Project>
   <ItemGroup>
     <PackageReference Include="Microsoft.DotNet.CodeAnalysis" Version="$(MicrosoftDotNetCodeAnalysisPackageVersion)" />
-    <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="3.3.0-beta1-final" />
+    <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="3.3.0-beta2-final" />
     <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="2.9.4" />
-    <PackageReference Include="StyleCop.Analyzers" Version="1.1.118" />
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.66" />
   </ItemGroup>
 </Project>