Wrong Simulator Detection

https://github.com/agens-no/EllipticCurveKeyPair/blob/944ae5c89ca045e9f1a113b736706c73fc51d1c2/Sources/EllipticCurveKeyPair.swift#L830

Please use something like this:
```
#if targetEnvironment(simulator)
// for sim only
#else
// for device
#endif
```