Simplify signing.props (#33554)
Simplify signing.props (#33554)

We don't need a target to set this property since Signing.props
will be imported after the default(false) is set.
ptoonen/corefx,shimingsg/corefx,BrennanConroy/corefx,ptoonen/corefx,ericstj/corefx,ptoonen/corefx,ptoonen/corefx,ericstj/corefx,ericstj/corefx,shimingsg/corefx,wtgodbe/corefx,ViktorHofer/corefx,wtgodbe/corefx,ViktorHofer/corefx,ViktorHofer/corefx,ericstj/corefx,wtgodbe/corefx,wtgodbe/corefx,shimingsg/corefx,ptoonen/corefx,shimingsg/corefx,ericstj/corefx,wtgodbe/corefx,shimingsg/corefx,shimingsg/corefx,ericstj/corefx,ptoonen/corefx,ptoonen/corefx,BrennanConroy/corefx,ViktorHofer/corefx,BrennanConroy/corefx,ericstj/corefx,wtgodbe/corefx,ViktorHofer/corefx,ViktorHofer/corefx,shimingsg/corefx,ViktorHofer/corefx,wtgodbe/corefx