$PropertyType fails on extended class

This is a:

- [x] Bug Report

Which concerns:

- [x] flow-runtime
---

### What is the current behaviour?

I am trying to use `$PropertyType` to check the property of an extended class. The following code illustrates the issue:
```
class AbstractClass {
prop: any;
};

type ClassProp = $PropertyType;

class ConcreteClass extends AbstractClass {
prop: number;
}

const i = 12;
(i: ClassProp);
```
Running this example in the Try Flow-Runtime interface throws the following error: `Can only intersect object types`.

---

### What is the expected behaviour?

Parity with Flow: The same code [runs without errors in Flow](https://flow.org/try/#0MYGwhgzhAECCBGEAuAnMwkGFxWgbwChpoBIABxQHsyAuaMAOwE8BuAgXzYKSbIFNo2SBAAKVMgB5sALzoJkaDEKgA+aAF5oAEjHU+KHgBVefKSGkAaaAHIK1ayq6hhgyg2Ao+SPsph8AHt4MACYw8qjoWDgwhMTk4nQMAK4AtvD6bOwEBMBuyNAAlhrQAIwATGwAFAV0vrqSmG4eXj7RKgCULEA)

It also [correctly errors on failures against the extended type](https://flow.org/try/#0MYGwhgzhAECCBGEAuAnMwkGFxWgbwChpoBIABxQHsyAuaMAOwE8BuAgXzYKSbIFNo2SBAAKVMgB5sALzoJkaDEKgA+aAF5oAEjHU+KHgBVefKSGkAaaAHIK1ayq6hhgyg2Ao+SPsph8AHt4MACYw8qjoWDgwhMTk4nQMAK4AtvD6bOwEBMBuyNAAlho2AGaUlNZsABQFdL66kphuHl4+0SoAlCxAA).

---

### Which package versions are you using?

Tried in the current Try Flow-Runtime interface, assuming this is `v0.17.0`