Deprecate Appveyor CI (onnx#2736)

* Deprecate appveyor builds now that azure-pipelines CI is working for Windows

* adding azure pipelines logo

Author: vinitra

README.md

@@ -1,8 +1,7 @@
 <p align="center"><img width="40%" src="docs/ONNX_logo_main.png" /></p>
 
 [![Build Status](https://img.shields.io/travis/onnx/onnx/master.svg?label=Linux)](https://travis-ci.org/onnx/onnx)
-[![Build status](https://img.shields.io/appveyor/ci/onnx/onnx/master.svg?label=Windows)](https://ci.appveyor.com/project/onnx/onnx)
-[![Build Status](https://dev.azure.com/onnx-pipelines/onnx/_apis/build/status/Windows-CI?branchName=master)](https://dev.azure.com/onnx-pipelines/onnx/_build/latest?definitionId=5&branchName=master)
+[![Build Status](https://img.shields.io/azure-devops/build/onnx-pipelines/onnx/5?label=Windows&logo=Azure-Pipelines)](https://dev.azure.com/onnx-pipelines/onnx/_build/latest?definitionId=5&branchName=master)
 [![Build Status](https://img.shields.io/jenkins/s/http/powerci.osuosl.org/onnx-ppc64le-nightly-build.svg?label=Linux%20ppc64le)](http://powerci.osuosl.org/job/onnx-ppc64le-nightly-build/)
 
 [Open Neural Network Exchange (ONNX)](https://onnx.ai) is an open ecosystem that empowers AI developers