Remove appveyor.yml and correct typos in the build pipeline from V2, V3, V4 #2898
Description
Currently, the dev, v3.x, and v4.x branches contain appveyor.yml, which is the outdated build pipeline for Core Tools V1, originally hosted on AppVeyor. We have moved the pipeline to Azure DevOps, and as such appveyor.yml (and all references to AppVeyor in azure-pipelines.yml) should be removed from these branches.