[PySide] Pyside configuration error

[Michael Hill]

I'm not sure if this is valid, but sources/pyside2/CMakeLists.txt was
half the size for 5.14.1 as it was for 5.12.1. I patched in the
missing lines and changed this line to 5.14:

find_package(Qt5 5.12 REQUIRED COMPONENTS Core)

allowing the build to complete. I'm just waiting for the rest of the
Flatpak to finish building to test the resulting FreeCAD.

Mike