[appveyor] Stop installing TAEF (#862)

Appveyor already has WDK for Windows 10, version 1709 installed:
https://www.appveyor.com/docs/build-environment/

appveyor.yml

@@ -12,8 +12,7 @@ environment:
   HLSL_BLD_DIR: c:\projects\DirectXShaderCompiler\build
 
 install:
-- ps: c:\projects\DirectXShaderCompiler\utils\appveyor\appveyor_setup.ps1
-- git submodule update --init --recursive
+- cmd: git submodule update --init
 
 before_build:
 - cmd: call utils\hct\hctstart %HLSL_SRC_DIR% %HLSL_BLD_DIR%
@@ -22,7 +21,7 @@ build_script:
 - cmd: call utils\hct\hctbuild -%PLATFORM% -%CONFIGURATION% -vs2017 -spirvtest
 
 test_script:
-- cmd: powershell utils\appveyor\appveyor_test.ps1
+- ps:  utils\appveyor\appveyor_test.ps1
 - cmd: call utils\hct\hcttest spirv_only
 
 after_test:

utils/appveyor/appveyor_setup.ps1

@@ -1,12 +0,0 @@
-$ErrorActionPreference = "Stop"
-# Install TAEF binaries.
-$http="https://github.com/Microsoft/WinObjC/raw/develop/deps/prebuilt/nuget/taef.redist.wlk.1.0.170206001-nativetargets.nupkg"
-$tempFile="$env:TEMP\taef.zip"
-Write-Host "Downloading TAEF to $tempFile"
-Invoke-WebRequest $http -OutFile $tempFile
-
-$taefDir = "$env:HLSL_SRC_DIR\external\taef"
-Write-Host "Extracting TAEF to $taefDir"
-Expand-Archive -Path $tempFile -DestinationPath $taefDir -Force
-
-Write-Host "TAEF setup completed successfully"