gr example depends on Qt4

[treygreer]

The gr example gives me
GKS: libQtGui.so.4: cannot open shared object file: No such file or directory

I'm on CentOS 8 where Qt4 is not readily available. The Plots GR code in general no longer depends on Qt4, so this is a bit of a mystery. I'm digging into it, but any hints would be greatly appreciated. Thanks!

[treygreer]

Seems the fix is to add ENV["GKS_QT_VERSION"]=5 to gr.jl. I'll submit a pull request shortly.

[ufechner7]

With QML 0.8 the example just works.