GBDevice: Do not unset firmware from dynamic state

It is not clear why this was being done, but it is the source of issues
for multiple devices, since the ensureDeviceUpToDate function will
attempt to persist the null values, in non-nullable columns.

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/impl/GBDevice.java

@@ -400,15 +400,12 @@ public class GBDevice implements Parcelable {
     }
 
     private void unsetDynamicState() {
-
         setBatteryLevel(BATTERY_UNKNOWN, 0);
         setBatteryLevel(BATTERY_UNKNOWN, 1);
         setBatteryLevel(BATTERY_UNKNOWN, 2);
         setBatteryState(UNKNOWN, 0);
         setBatteryState(UNKNOWN, 1);
         setBatteryState(UNKNOWN, 2);
-        setFirmwareVersion(null);
-        setFirmwareVersion2(null);
         setRssi(RSSI_UNKNOWN);
         resetExtraInfos();
         if (mBusyTask != null) {