Remove travix + assveyor.

Readme.md

@@ -4,8 +4,6 @@ A library to import and export various 3d-model-formats including scene-post-pro
 ### Current project status ###
 [![Financial Contributors on Open Collective](https://opencollective.com/assimp/all/badge.svg?label=financial+contributors)](https://opencollective.com/assimp) 
 ![C/C++ CI](https://github.com/assimp/assimp/workflows/C/C++%20CI/badge.svg)
-[![Linux Build Status](https://travis-ci.org/assimp/assimp.svg)](https://travis-ci.org/assimp/assimp)
-[![Windows Build Status](https://ci.appveyor.com/api/projects/status/tmo433wax6u6cjp4?svg=true)](https://ci.appveyor.com/project/kimkulling/assimp)
 <a href="https://scan.coverity.com/projects/5607">
   <img alt="Coverity Scan Build Status"
        src="https://scan.coverity.com/projects/5607/badge.svg"/>