README: Remove deprecated Appveyor badge [skip ci]

README.md

@@ -8,7 +8,6 @@ build system.
 
 [![PyPI](https://img.shields.io/pypi/v/meson.svg)](https://pypi.python.org/pypi/meson)
 [![Travis](https://travis-ci.org/mesonbuild/meson.svg?branch=master)](https://travis-ci.org/mesonbuild/meson)
-[![Appveyor](https://ci.appveyor.com/api/projects/status/7jfaotriu8d8ncov?svg=true)](https://ci.appveyor.com/project/mesonbuild/meson)
 [![Build Status](https://dev.azure.com/jussi0947/jussi/_apis/build/status/mesonbuild.meson)](https://dev.azure.com/jussi0947/jussi/_build/latest?definitionId=1)
 [![Codecov](https://codecov.io/gh/mesonbuild/meson/coverage.svg?branch=master)](https://codecov.io/gh/mesonbuild/meson/branch/master)
 [![Code Quality: Python](https://img.shields.io/lgtm/grade/python/g/mesonbuild/meson.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/mesonbuild/meson/context:python)