Add comment for updating version

Author: edvilme

eng/Versions.props

@@ -64,6 +64,7 @@
     <MicrosoftVisualBasicVersion>10.3.0</MicrosoftVisualBasicVersion>
     <MicrosoftVisualStudioSetupConfigurationInteropVersion>3.2.2146</MicrosoftVisualStudioSetupConfigurationInteropVersion>
     <MicrosoftWindowsCsWin32PackageVersion>0.3.49-beta</MicrosoftWindowsCsWin32PackageVersion>
+    <!-- When updating make sure to sync with dotnet/msbuild and NuGet/NuGet.Client -->
     <MicrosoftVisualStudioSolutionPersistenceVersion>1.0.52</MicrosoftVisualStudioSolutionPersistenceVersion>
   </PropertyGroup>
   <PropertyGroup Label="NUnit3.DotNetNew.Template version">