Unexpected ".0" added to firmware revision number
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**Describe The Bug:**
When I (as plug-in developer) set the Firmware Revision to an integer number the Home App appends ".0" to that integer.

```
service.setCharacteristic(this.Characteristic.FirmwareRevision, 123)
```

Home App will show:

```
Firmware 123.0
```

**To Reproduce:**
Write a minimal plugin that only sets the Firmware Revision on the Accessory Information service to an integer number.

**Expected behavior:**
Home App displays the specified integer number (without the ".0" suffix):

```
Firmware 123
```

**Logs:**
n/a

**Homebridge Config:**
n/a

**Screenshots:**
n/a

**Environment:**

* **Node.js Version**: 14.17.0
* **NPM Version**: 7.15.0
* **Homebridge Version**: 1.3.4
* **Operating System**: Raspbian 
* **Process Supervisor**: hb-service