Add ppb as a valid uom for sensor/number NO2 device class (#2902)

Author: Thomas55555

docs/core/entity/number.md

@@ -56,7 +56,7 @@ If specifying a device class, your number entity will need to also return the co
 | `NumberDeviceClass.IRRADIANCE` | W/m², BTU/(h⋅ft²) | Irradiance
 | `NumberDeviceClass.MOISTURE` | % | Moisture
 | `NumberDeviceClass.MONETARY` | [ISO 4217](https://en.wikipedia.org/wiki/ISO_4217#Active_codes) | Monetary value with a currency.
-| `NumberDeviceClass.NITROGEN_DIOXIDE` | µg/m³ | Concentration of nitrogen dioxide
+| `NumberDeviceClass.NITROGEN_DIOXIDE` | ppb, µg/m³ | Concentration of nitrogen dioxide
 | `NumberDeviceClass.NITROGEN_MONOXIDE` | µg/m³ | Concentration of nitrogen monoxide
 | `NumberDeviceClass.NITROUS_OXIDE` | µg/m³ | Concentration of nitrous oxide
 | `NumberDeviceClass.OZONE` | µg/m³ | Concentration of ozone

docs/core/entity/sensor.md

@@ -59,7 +59,7 @@ If specifying a device class, your sensor entity will need to also return the co
 | `SensorDeviceClass.IRRADIANCE` | W/m², BTU/(h⋅ft²) | Irradiance
 | `SensorDeviceClass.MOISTURE` | % | Moisture
 | `SensorDeviceClass.MONETARY` | [ISO 4217](https://en.wikipedia.org/wiki/ISO_4217#Active_codes) | Monetary value with a currency.
-| `SensorDeviceClass.NITROGEN_DIOXIDE` | µg/m³ | Concentration of nitrogen dioxide
+| `SensorDeviceClass.NITROGEN_DIOXIDE` | ppb, µg/m³ | Concentration of nitrogen dioxide
 | `SensorDeviceClass.NITROGEN_MONOXIDE` | µg/m³ | Concentration of nitrogen monoxide
 | `SensorDeviceClass.NITROUS_OXIDE` | µg/m³ | Concentration of nitrous oxide
 | `SensorDeviceClass.OZONE` | µg/m³ | Concentration of ozone