Disable broken Appveyor integration

[AiyionPrime]

@locka99 would it be possible to disable the apparently misconfigured Appveyor integration?
Currently it flags all PRs as failing.

Build started
git clone -q https://github.com/locka99/opcua.git C:\projects\opcua
git fetch -q origin +refs/pull/330/merge:
git checkout -qf FETCH_HEAD
The build phase is set to "MSBuild" mode (default), but no Visual Studio project or solution files were found in the root directory. If you are not building Visual Studio project switch build mode to "Script" and provide your custom build command.

from https://ci.appveyor.com/project/locka99/opcua/builds/50033620

[AiyionPrime]

@locka99 Is the remaining work for the removal of appveyor as easy as removing the webhook from this repos settings?

[AiyionPrime]

@locka99 I think this is would be the page: https://github.com/locka99/opcua/settings/hooks

As soon as you remove the webhook for AppVeyor, it should cease assessing and failing every build.