build: cleanup some unnecessary settings for Windows
build: cleanup some unnecessary settings for Windows

Windows had moved to C++14 much earlier than the rest of Swift.  This
was required in order to deal with the Windows SDK headers.  Now that
the project has fully moved to C++14, remove the unnecessary settings
for Windows.

tkremenek/swift,hooman/swift,parkera/swift,harlanhaskins/swift,tkremenek/swift,benlangmuir/swift,atrick/swift,jckarter/swift,allevato/swift,atrick/swift,tkremenek/swift,ahoppen/swift,atrick/swift,airspeedswift/swift,xwu/swift,JGiola/swift,nathawes/swift,xwu/swift,jckarter/swift,JGiola/swift,hooman/swift,gregomni/swift,parkera/swift,JGiola/swift,JGiola/swift,tkremenek/swift,stephentyrone/swift,stephentyrone/swift,roambotics/swift,hooman/swift,tkremenek/swift,xwu/swift,apple/swift,apple/swift,atrick/swift,ahoppen/swift,roambotics/swift,CodaFi/swift,stephentyrone/swift,stephentyrone/swift,jckarter/swift,glessard/swift,CodaFi/swift,apple/swift,airspeedswift/swift,rudkx/swift,harlanhaskins/swift,allevato/swift,xwu/swift,nathawes/swift,harlanhaskins/swift,jmgc/swift,glessard/swift,jckarter/swift,parkera/swift,gregomni/swift,jmgc/swift,roambotics/swift,benlangmuir/swift,jmgc/swift,tkremenek/swift,jmgc/swift,harlanhaskins/swift,nathawes/swift,harlanhaskins/swift,nathawes/swift,benlangmuir/swift,gregomni/swift,glessard/swift,benlangmuir/swift,parkera/swift,nathawes/swift,allevato/swift,xwu/swift,nathawes/swift,jmgc/swift,allevato/swift,CodaFi/swift,rudkx/swift,CodaFi/swift,atrick/swift,gregomni/swift,glessard/swift,gregomni/swift,harlanhaskins/swift,ahoppen/swift,CodaFi/swift,harlanhaskins/swift,roambotics/swift,stephentyrone/swift,rudkx/swift,airspeedswift/swift,parkera/swift,jckarter/swift,atrick/swift,hooman/swift,glessard/swift,parkera/swift,rudkx/swift,hooman/swift,roambotics/swift,hooman/swift,apple/swift,allevato/swift,ahoppen/swift,airspeedswift/swift,hooman/swift,ahoppen/swift,parkera/swift,benlangmuir/swift,glessard/swift,airspeedswift/swift,rudkx/swift,jmgc/swift,xwu/swift,xwu/swift,allevato/swift,roambotics/swift,JGiola/swift,airspeedswift/swift,CodaFi/swift,jckarter/swift,apple/swift,benlangmuir/swift,allevato/swift,JGiola/swift,parkera/swift,rudkx/swift,airspeedswift/swift,jmgc/swift,stephentyrone/swift,jckarter/swift,gregomni/swift,ahoppen/swift,tkremenek/swift,CodaFi/swift,nathawes/swift,apple/swift,stephentyrone/swift