Update appveyor.yml

appveyor.yml

@@ -13,6 +13,3 @@ build:
   project: MQTTnet.sln
   verbosity: minimal
 
-test_script:
-- cmd: dotnet vstest "%APPVEYOR_BUILD_FOLDER%\Tests\MQTTnet.Core.Tests\bin\Release\netcoreapp3.1\MQTTnet.Tests.dll"
-- cmd: dotnet vstest "%APPVEYOR_BUILD_FOLDER%\Tests\MQTTnet.AspNetCore.Tests\bin\Release\netcoreapp3.1\MQTTnet.AspNetCore.Tests.dll"