Update .NET version in AppVeyor build (#423)

Author: pascalberger

.appveyor.yml

@@ -11,8 +11,8 @@ install:
   - ps: mkdir $env:DOTNET_INSTALL_DIR -Force | Out-Null
   - ps: Invoke-WebRequest -Uri "https://dotnet.microsoft.com/download/dotnet/scripts/v1/dotnet-install.ps1" -OutFile "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1"
   - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 5.0.408 -InstallDir $env:DOTNET_INSTALL_DIR'
-  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 6.0.412 -InstallDir $env:DOTNET_INSTALL_DIR'
-  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 7.0.306 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 6.0.413 -InstallDir $env:DOTNET_INSTALL_DIR'
+  - ps: '& "$($env:DOTNET_INSTALL_DIR)/dotnet-install.ps1" -Version 7.0.400 -InstallDir $env:DOTNET_INSTALL_DIR'
   - ps: $env:Path = "$env:DOTNET_INSTALL_DIR;$env:Path"
   - ps: dotnet --info