Add comment about roslyn manual updates

Author: akoeplinger

eng/Versions.props

@@ -157,6 +157,7 @@
     <MicrosoftEntityFrameworkCoreVersion>10.0.0-preview.4.25223.119</MicrosoftEntityFrameworkCoreVersion>
     <MicrosoftEntityFrameworkCoreDesignVersion>10.0.0-preview.4.25223.119</MicrosoftEntityFrameworkCoreDesignVersion>
     <!-- Packages from dotnet/roslyn -->
+    <!-- Not updated automatically -->
     <MicrosoftCodeAnalysisCommonVersion>4.13.0-3.24613.7</MicrosoftCodeAnalysisCommonVersion>
     <MicrosoftCodeAnalysisExternalAccessAspNetCoreVersion>4.13.0-3.24613.7</MicrosoftCodeAnalysisExternalAccessAspNetCoreVersion>
     <MicrosoftCodeAnalysisCSharpVersion>4.13.0-3.24613.7</MicrosoftCodeAnalysisCSharpVersion>