[AST] Drop unnecessary friend declaration
[AST] Drop unnecessary friend declaration

Summary:
The friend declaration wasn't qualified (it should have included the
namespace, i.e. `syntax::LegacyASTTransformer`). The effect was instead
to declare a `LegacyASTTransformer` inside the `swift` namespace, which
would then trip up Windows compilation because of non-conforming
two-phase lookup. The implication is that the friend declaration is
actually unneeded, since the incorrect declaration wasn't causing any
other problems, so we can just drop it.

lorentey/swift,ahoppen/swift,alblue/swift,danielmartin/swift,gregomni/swift,stephentyrone/swift,roambotics/swift,zisko/swift,austinzheng/swift,stephentyrone/swift,nathawes/swift,benlangmuir/swift,gribozavr/swift,gregomni/swift,xedin/swift,roambotics/swift,OscarSwanros/swift,CodaFi/swift,lorentey/swift,airspeedswift/swift,tkremenek/swift,jckarter/swift,alblue/swift,gribozavr/swift,amraboelela/swift,sschiau/swift,xedin/swift,aschwaighofer/swift,harlanhaskins/swift,practicalswift/swift,brentdax/swift,tkremenek/swift,shahmishal/swift,frootloops/swift,danielmartin/swift,karwa/swift,devincoughlin/swift,practicalswift/swift,jckarter/swift,hooman/swift,huonw/swift,xwu/swift,apple/swift,gribozavr/swift,lorentey/swift,nathawes/swift,shahmishal/swift,devincoughlin/swift,devincoughlin/swift,tjw/swift,amraboelela/swift,gribozavr/swift,aschwaighofer/swift,jckarter/swift,nathawes/swift,amraboelela/swift,allevato/swift,tkremenek/swift,tjw/swift,austinzheng/swift,zisko/swift,apple/swift,huonw/swift,karwa/swift,lorentey/swift,airspeedswift/swift,apple/swift,JGiola/swift,CodaFi/swift,jmgc/swift,frootloops/swift,tkremenek/swift,swiftix/swift,xedin/swift,shajrawi/swift,karwa/swift,karwa/swift,aschwaighofer/swift,parkera/swift,practicalswift/swift,practicalswift/swift,jckarter/swift,parkera/swift,glessard/swift,roambotics/swift,parkera/swift,CodaFi/swift,atrick/swift,hooman/swift,roambotics/swift,roambotics/swift,natecook1000/swift,devincoughlin/swift,rudkx/swift,tjw/swift,atrick/swift,xwu/swift,ahoppen/swift,practicalswift/swift,benlangmuir/swift,tjw/swift,frootloops/swift,allevato/swift,airspeedswift/swift,gregomni/swift,alblue/swift,harlanhaskins/swift,zisko/swift,gregomni/swift,xedin/swift,jmgc/swift,alblue/swift,devincoughlin/swift,harlanhaskins/swift,austinzheng/swift,practicalswift/swift,brentdax/swift,alblue/swift,danielmartin/swift,hooman/swift,gribozavr/swift,sschiau/swift,xedin/swift,frootloops/swift,benlangmuir/swift,benlangmuir/swift,xwu/swift,lorentey/swift,benlangmuir/swift,allevato/swift,shahmishal/swift,allevato/swift,jopamer/swift,jmgc/swift,airspeedswift/swift,shahmishal/swift,allevato/swift,gribozavr/swift,airspeedswift/swift,benlangmuir/swift,sschiau/swift,ahoppen/swift,parkera/swift,shajrawi/swift,tkremenek/swift,aschwaighofer/swift,jopamer/swift,sschiau/swift,natecook1000/swift,hooman/swift,stephentyrone/swift,parkera/swift,apple/swift,shajrawi/swift,sschiau/swift,xwu/swift,nathawes/swift,CodaFi/swift,atrick/swift,jckarter/swift,allevato/swift,parkera/swift,tkremenek/swift,hooman/swift,jopamer/swift,swiftix/swift,airspeedswift/swift,devincoughlin/swift,amraboelela/swift,CodaFi/swift,ahoppen/swift,sschiau/swift,apple/swift,austinzheng/swift,natecook1000/swift,swiftix/swift,karwa/swift,austinzheng/swift,xwu/swift,OscarSwanros/swift,huonw/swift,hooman/swift,nathawes/swift,glessard/swift,OscarSwanros/swift,glessard/swift,stephentyrone/swift,CodaFi/swift,austinzheng/swift,ahoppen/swift,shahmishal/swift,karwa/swift,OscarSwanros/swift,huonw/swift,aschwaighofer/swift,swiftix/swift,harlanhaskins/swift,brentdax/swift,parkera/swift,devincoughlin/swift,atrick/swift,shahmishal/swift,atrick/swift,shajrawi/swift,shajrawi/swift,danielmartin/swift,atrick/swift,lorentey/swift,tjw/swift,danielmartin/swift,alblue/swift,brentdax/swift,stephentyrone/swift,jopamer/swift,glessard/swift,amraboelela/swift,huonw/swift,stephentyrone/swift,lorentey/swift,natecook1000/swift,OscarSwanros/swift,OscarSwanros/swift,swiftix/swift,xwu/swift,huonw/swift,hooman/swift,zisko/swift,xedin/swift,swiftix/swift,xwu/swift,allevato/swift,JGiola/swift,tkremenek/swift,brentdax/swift,JGiola/swift,amraboelela/swift,ahoppen/swift,jopamer/swift,jmgc/swift,amraboelela/swift,stephentyrone/swift,aschwaighofer/swift,shajrawi/swift,harlanhaskins/swift,swiftix/swift,shajrawi/swift,karwa/swift,frootloops/swift,harlanhaskins/swift,jckarter/swift,nathawes/swift,gregomni/swift,CodaFi/swift,rudkx/swift,rudkx/swift,gribozavr/swift,devincoughlin/swift,jmgc/swift,brentdax/swift,brentdax/swift,rudkx/swift,nathawes/swift,shajrawi/swift,JGiola/swift,frootloops/swift,parkera/swift,practicalswift/swift,huonw/swift,rudkx/swift,zisko/swift,tjw/swift,glessard/swift,xedin/swift,natecook1000/swift,gregomni/swift,shahmishal/swift,jmgc/swift,danielmartin/swift,natecook1000/swift,harlanhaskins/swift,natecook1000/swift,xedin/swift,alblue/swift,zisko/swift,sschiau/swift,JGiola/swift,lorentey/swift,glessard/swift,apple/swift,gribozavr/swift,sschiau/swift,roambotics/swift,airspeedswift/swift,frootloops/swift,rudkx/swift,JGiola/swift,tjw/swift,danielmartin/swift,zisko/swift,jopamer/swift,OscarSwanros/swift,practicalswift/swift,aschwaighofer/swift,austinzheng/swift,shahmishal/swift,karwa/swift,jopamer/swift,jmgc/swift,jckarter/swift