shouldm't have changed AppVeyor's own uris

Author: bodewig

appveyor.yml

@@ -12,7 +12,7 @@ for:
         - image: Visual Studio 2013
     before_build:
       - appveyor DownloadFile https://dist.nuget.org/win-x86-commandline/v4.9.2/nuget.exe
-      - appveyor DownloadFile https://raw.githubusercontent.com/appveyor/ci/main/scripts/nuget-restore.cmd
+      - appveyor DownloadFile https://raw.githubusercontent.com/appveyor/ci/master/scripts/nuget-restore.cmd
       - nuget-restore XMLUnit.NET.NetFramework.sln
     cache:
       - packages -> **\packages.config