WriteTo:ConditionalSink does not work in sample application

[edespong]

According to https://github.com/serilog/serilog-settings-configuration/issues/293#issuecomment-1002972481 the 'New expression package uses shorter syntax (CLEF) for expressions.'

as such, the WriteTo:ConditionalSink sink in sample application does not work as expected. @Level should be @l

"WriteTo:ConditionalSink": {
      "Name": "Conditional",
      "Args": {
        "expression": "@Level in ['Error', 'Fatal']",
        "configureSink": [
          {
            "Name": "File",
            "Args": {
              "path": "%TEMP%/Logs/serilog-configuration-sample-errors.txt",
              "formatter": {
                "type": "Serilog.Formatting.Compact.CompactJsonFormatter, Serilog.Formatting.Compact",
                "valueFormatter": {
                  "typeTagName": "customTypeTag"
                }
              }
            }
          }
        ]
      }
    }

https://github.com/serilog/serilog-settings-configuration/blob/dev/sample/Sample/appsettings.json#L49