factory-south-win7 - Disable nightly windows 32-bit release

Waiting the work of Brad Lowekamp regarding the speedup of the SimpleITK
build  is integrated to Slicer and SimpleITK, disable the nightly windows
32-bit release because it doesn't have time to complete before noon.

See https://github.com/blowekamp/Slicer/tree/SimpleITKAsSharedLibrary