chore(deps): update dependency microsoft.codeanalysis.csharp to 4.12.0

Author: renovate[bot]

src/ReactiveMarbles.RoslynHelpers/ReactiveMarbles.RoslynHelpers.csproj

@@ -19,7 +19,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.10.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.12.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>