Update .NET version in appveyor.yml to 10.0.200

Author: snakefoot

appveyor.yml

@@ -17,7 +17,7 @@ environment:
 install:
 - ps: |
     Invoke-WebRequest -Uri 'https://dot.net/v1/dotnet-install.ps1' -UseBasicParsing -OutFile "$env:temp\dotnet-install.ps1"
-    & $env:temp\dotnet-install.ps1 -Architecture x64 -Version '10.0.100' -InstallDir "$env:ProgramFiles\dotnet"
+    & $env:temp\dotnet-install.ps1 -Architecture x64 -Version '10.0.200' -InstallDir "$env:ProgramFiles\dotnet"
 
 build_script:
   - ps: .\build.ps1