Reduce the appveyor CI tasks

[sokra]

What kind of change does this PR introduce?
CI

Did you add tests for your changes?
N/A

Does this PR introduce a breaking change?
N/A

What needs to be documented once your changes are merged?
nothing

[webpack-bot]

For maintainers only:

• This need to be documented (issue in webpack/webpack.js.org will be filed when merged)

[webpack-bot]

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