sensor: add relative humidity

Change-Id: I84f37194adbcaf99b4c426a8d51afc738bd6a799
diff --git a/yaml/xyz/openbmc_project/Sensor/Threshold/Warning.interface.yaml b/yaml/xyz/openbmc_project/Sensor/Threshold/Warning.interface.yaml
index aa5d989..3226862 100644
--- a/yaml/xyz/openbmc_project/Sensor/Threshold/Warning.interface.yaml
+++ b/yaml/xyz/openbmc_project/Sensor/Threshold/Warning.interface.yaml
@@ -7,6 +7,7 @@
       current
       energy
       fan_tach
+      humidity
       power
       pressure
       temperature