devel/qtscriptgenerator : switch from GOOGLE_CODE to USE_GITHUB

In r422140 devel/qtscriptgenerator was marked BROKEN, as GOOGLE_CODE
has gone swimming with the fishes.

The project is available on github via qt-labs projects [1] which seems
reasonably official.

The only difference in the distfile created by this, is that the Copyright
holder changes from 'nokia' to 'digia'.

[1] https://github.com/qt-labs/qtscriptgenerator

Approved by: mat (mentor)
PR: 212789