Update AutoRest C# version (Azure#18125)

Update AutoRest C# version to 3.0.0-beta.20210121.3

Author: azure-sdk

eng/Packages.Data.props

@@ -119,7 +119,7 @@
     All should have PrivateAssets="All" set so they don't become pacakge dependencies
   -->
   <ItemGroup>
-    <PackageReference Update="Microsoft.Azure.AutoRest.CSharp" Version="3.0.0-beta.20210121.2" PrivateAssets="All" />
+    <PackageReference Update="Microsoft.Azure.AutoRest.CSharp" Version="3.0.0-beta.20210121.3" PrivateAssets="All" />
     <PackageReference Update="Azure.ClientSdk.Analyzers" Version="0.1.1-dev.20200929.2" PrivateAssets="All" />
     <PackageReference Update="coverlet.collector" Version="1.3.0" PrivateAssets="All" />
     <PackageReference Update="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="3.3.1" PrivateAssets="All" />