Upgrade to onnx 1.6.0

Author: antoniovs1029

NuGet.config

@@ -14,7 +14,6 @@
     <add key="myget-roslyn" value="https://dotnet.myget.org/F/roslyn-analyzers/api/v3/index.json" />
     <add key="mlnet-daily" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/MachineLearning/nuget/v3/index.json" />
     <add key="mlnet-testdata" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/machinelearning-testdata/nuget/v3/index.json" />
-    <add key="onnx-prerelease" value="https://aiinfra.pkgs.visualstudio.com/PublicPackages/_packaging/ORT-Nightly/nuget/v3/index.json" />
   </packageSources>
   <disabledPackageSources>
     <clear />

eng/Versions.props

@@ -23,7 +23,7 @@
     <GoogleProtobufPackageVersion>3.10.1</GoogleProtobufPackageVersion>
     <LightGBMPackageVersion>2.2.3</LightGBMPackageVersion>
     <MicrosoftExtensionsPackageVersion>2.1.0</MicrosoftExtensionsPackageVersion>
-    <MicrosoftMLOnnxRuntimePackageVersion>1.5.2-dev-20201204-0513-14f6eb14</MicrosoftMLOnnxRuntimePackageVersion>
+    <MicrosoftMLOnnxRuntimePackageVersion>1.6.0</MicrosoftMLOnnxRuntimePackageVersion>
     <MlNetMklDepsPackageVersion>0.0.0.9</MlNetMklDepsPackageVersion>
     <ParquetDotNetPackageVersion>2.1.3</ParquetDotNetPackageVersion>
     <SystemDrawingCommonPackageVersion>4.5.0</SystemDrawingCommonPackageVersion>