Update of PyQt5 imports needed.

In recent _PyQt5_ releases, the `QtWebKit` module has been replaced by `QtWebEngine`.
This causes the following error to occur when attempting to use the most recent PyQt5 release:

```
File "/Users/dbanas/Documents/Projects/PyBERT/pyface/pyface/qt/QtWebKit.py", line 18, in
from PyQt5.QtWebKit import *
ModuleNotFoundError: No module named 'PyQt5.QtWebKit'
```

So, 2 questions:

1. Are there plans to update _PyFace_ to use `QtWebEngine`, instead of `QtWebKit`?

1. Do you happen to know in which release of PyQt5 this change first occurred?

Thanks!