fix: Apc humidity sensors negative value filtering (#8743)

Hello

We have  PDUs (APC) that were returning "-1" as Humidity value, and it seems that this happens when the optional humidity sensor is not plugged into the PDU. 
This PR is adding a check to skip the negative values.

Bye
PipoCanaja

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includes/definitions/discovery/apc.yaml

@@ -321,6 +321,10 @@ modules:
                         oid: rPDU2SensorTempHumidityStatusType
                         op: '='
                         value: 4
+                      - 
+                        oid: rPDU2SensorTempHumidityStatusRelativeHumidity
+                        op: '<'
+                        value: 0
         airflow:
             data:
                 -