Stop using choco for .net5 install (#3388)

Author: rli

buildspec/windowsTests.yml

@@ -27,7 +27,9 @@ phases:
       - choco uninstall -y dotnet-sdk --version 5.0.100 dotnet-5.0-sdk --version 5.0.100
       - "Remove-Item -Recurse -Force 'C:\\Program\ Files\\dotnet\\sdk\\5.0.100'"
       - "Remove-Item -Recurse -Force 'C:\\Program\ Files\\dotnet\\sdk\\6.0.202'"
-      - choco install -y dotnet-5.0-sdk
+      - |
+        Invoke-WebRequest 'https://dot.net/v1/dotnet-install.ps1' -OutFile 'dotnet-install.ps1';
+        ./dotnet-install.ps1 -Verbose -InstallDir 'C:\Program Files\dotnet' -Channel '5.0'
       - dotnet --list-sdks
 
   build: