remove appveyor.yml and appveyor badge

Author: astanin

README.md

@@ -53,7 +53,7 @@ pip install tabulate
 Build status
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-[![python-tabulate](https://github.com/astanin/python-tabulate/actions/workflows/tabulate.yml/badge.svg)](https://github.com/astanin/python-tabulate/actions/workflows/tabulate.yml) [![Build status](https://ci.appveyor.com/api/projects/status/8745yksvvol7h3d7/branch/master?svg=true)](https://ci.appveyor.com/project/astanin/python-tabulate/branch/master)
+[![python-tabulate](https://github.com/astanin/python-tabulate/actions/workflows/tabulate.yml/badge.svg)](https://github.com/astanin/python-tabulate/actions/workflows/tabulate.yml)
 
 Library usage
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