Add comment to Packages.Data.Props for synchronizing SDK upgrades with autorest.csharp (Azure#48571)

Author: m-redding

eng/Packages.Data.props

@@ -253,6 +253,7 @@
     <PackageReference Update="Microsoft.Azure.AutoRest.CSharp" Version="3.0.0-beta.20250303.1" PrivateAssets="All" />
     <PackageReference Update="Azure.ClientSdk.Analyzers" Version="0.1.1-dev.20250227.2" PrivateAssets="All" />
     <PackageReference Update="coverlet.collector" Version="3.2.0" PrivateAssets="All" />
+    <!-- Note: Upgrading the .NET SDK version needs to be synchronized with the autorest.csharp repository -->
     <PackageReference Update="Microsoft.CodeAnalysis.NetAnalyzers" Version="9.0.0" PrivateAssets="All" />
     <PackageReference Update="Microsoft.CodeAnalysis.BannedApiAnalyzers" Version="3.3.2" PrivateAssets="All" />
     <PackageReference Update="Microsoft.DotNet.ApiCompat" Version="5.0.0-beta.20467.1" PrivateAssets="All" />