Bump Microsoft.CodeAnalysis.CSharp.Workspaces

Bumps [Microsoft.CodeAnalysis.CSharp.Workspaces](https://github.com/dotnet/roslyn) from 3.8.0 to 3.9.0.
- [Release notes](https://github.com/dotnet/roslyn/releases)
- [Changelog](https://github.com/dotnet/roslyn/blob/master/docs/Breaking%20API%20Changes.md)
- [Commits](dotnet/roslyn@v3.8.0...v3.9.0)

Signed-off-by: dependabot[bot] <support@github.com>

samples/snippets/csharp/roslyn-sdk/SyntaxQuickStart/SyntaxWalker/SyntaxWalker.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="3.8.0" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="3.9.0" />
   </ItemGroup>
 
 </Project>