docs: remove appveyor badge

Author: mgechev

README.md

@@ -1,7 +1,6 @@
 [![npm version](https://badge.fury.io/js/codelyzer.svg)](https://badge.fury.io/js/codelyzer)
 [![Downloads](https://img.shields.io/npm/dt/codelyzer.svg)](https://img.shields.io/npm/dt/codelyzer.svg)
 [![Build Status](https://travis-ci.org/mgechev/codelyzer.svg?branch=master)](https://travis-ci.org/mgechev/codelyzer)
-[![Build status](https://ci.appveyor.com/api/projects/status/7xj7qs0a0h0ald53?svg=true)](https://ci.appveyor.com/project/mgechev/codelyzer)
 [![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg?style=flat-square)](https://github.com/prettier/prettier)
 [![Conventional Commits](https://img.shields.io/badge/Conventional%20Commits-1.0.0-yellow.svg)](https://conventionalcommits.org)
 [![Gitter Chat](https://camo.githubusercontent.com/da2edb525cde1455a622c58c0effc3a90b9a181c/68747470733a2f2f6261646765732e6769747465722e696d2f4a6f696e253230436861742e737667)](https://gitter.im/mgechev/codelyzer)