".is<uint8_t>() == true" doesn't return true

The following code does not work with the latest version 7.4.1

```c++
 if (jsonDoc["pin"].is<uint8_t>() == true)
 {
  relayConfig.pin  = jsonDoc[F("pin")]; 
}
```

**Environment**  
Here is the environment that I used:
* Microcontroller: ESP8266
* Core/runtime: ESP8266 core for Arduino v3.0.2
* IDE: Arduino IDE 1.8.16
