Remove the unused TypeResolverFlags::ResolveStructure.
Remove the unused TypeResolverFlags::ResolveStructure.

I removed all uses of this in a previous pull request, but my
incorrect rebase onto master (following the introduction of 
TypeResolverContext) left the flag there. Remove it again. NFC
roambotics/swift,gribozavr/swift,CodaFi/swift,rudkx/swift,xedin/swift,allevato/swift,austinzheng/swift,lorentey/swift,ahoppen/swift,hooman/swift,airspeedswift/swift,tkremenek/swift,alblue/swift,practicalswift/swift,allevato/swift,brentdax/swift,allevato/swift,hooman/swift,karwa/swift,shahmishal/swift,JGiola/swift,parkera/swift,devincoughlin/swift,harlanhaskins/swift,atrick/swift,hooman/swift,hooman/swift,CodaFi/swift,harlanhaskins/swift,harlanhaskins/swift,glessard/swift,JGiola/swift,rudkx/swift,karwa/swift,hooman/swift,brentdax/swift,airspeedswift/swift,brentdax/swift,stephentyrone/swift,jmgc/swift,lorentey/swift,austinzheng/swift,nathawes/swift,benlangmuir/swift,rudkx/swift,amraboelela/swift,allevato/swift,karwa/swift,aschwaighofer/swift,gregomni/swift,gregomni/swift,airspeedswift/swift,sschiau/swift,shajrawi/swift,airspeedswift/swift,jmgc/swift,tkremenek/swift,parkera/swift,sschiau/swift,harlanhaskins/swift,stephentyrone/swift,rudkx/swift,alblue/swift,xedin/swift,roambotics/swift,parkera/swift,xwu/swift,ahoppen/swift,aschwaighofer/swift,JGiola/swift,xedin/swift,natecook1000/swift,allevato/swift,austinzheng/swift,amraboelela/swift,alblue/swift,amraboelela/swift,rudkx/swift,jmgc/swift,practicalswift/swift,aschwaighofer/swift,lorentey/swift,tkremenek/swift,glessard/swift,atrick/swift,amraboelela/swift,jckarter/swift,apple/swift,glessard/swift,ahoppen/swift,shajrawi/swift,roambotics/swift,nathawes/swift,parkera/swift,xwu/swift,devincoughlin/swift,CodaFi/swift,shahmishal/swift,stephentyrone/swift,devincoughlin/swift,gribozavr/swift,roambotics/swift,devincoughlin/swift,atrick/swift,parkera/swift,stephentyrone/swift,gribozavr/swift,lorentey/swift,natecook1000/swift,aschwaighofer/swift,apple/swift,lorentey/swift,gregomni/swift,atrick/swift,CodaFi/swift,jmgc/swift,sschiau/swift,brentdax/swift,sschiau/swift,alblue/swift,danielmartin/swift,jmgc/swift,natecook1000/swift,danielmartin/swift,nathawes/swift,devincoughlin/swift,stephentyrone/swift,lorentey/swift,karwa/swift,natecook1000/swift,shahmishal/swift,gribozavr/swift,shajrawi/swift,benlangmuir/swift,jckarter/swift,natecook1000/swift,danielmartin/swift,atrick/swift,shahmishal/swift,lorentey/swift,alblue/swift,xedin/swift,devincoughlin/swift,benlangmuir/swift,benlangmuir/swift,xedin/swift,nathawes/swift,JGiola/swift,jckarter/swift,sschiau/swift,xwu/swift,parkera/swift,practicalswift/swift,practicalswift/swift,shajrawi/swift,practicalswift/swift,benlangmuir/swift,practicalswift/swift,ahoppen/swift,brentdax/swift,karwa/swift,xwu/swift,gribozavr/swift,gregomni/swift,shahmishal/swift,devincoughlin/swift,sschiau/swift,harlanhaskins/swift,devincoughlin/swift,alblue/swift,allevato/swift,harlanhaskins/swift,hooman/swift,shajrawi/swift,CodaFi/swift,practicalswift/swift,JGiola/swift,shahmishal/swift,stephentyrone/swift,atrick/swift,jckarter/swift,karwa/swift,gribozavr/swift,karwa/swift,xedin/swift,aschwaighofer/swift,gregomni/swift,austinzheng/swift,shahmishal/swift,xedin/swift,gregomni/swift,rudkx/swift,xwu/swift,apple/swift,brentdax/swift,jckarter/swift,tkremenek/swift,allevato/swift,apple/swift,jmgc/swift,xwu/swift,airspeedswift/swift,danielmartin/swift,aschwaighofer/swift,xwu/swift,austinzheng/swift,sschiau/swift,parkera/swift,roambotics/swift,natecook1000/swift,roambotics/swift,gribozavr/swift,ahoppen/swift,stephentyrone/swift,tkremenek/swift,glessard/swift,CodaFi/swift,amraboelela/swift,alblue/swift,CodaFi/swift,apple/swift,aschwaighofer/swift,gribozavr/swift,shajrawi/swift,JGiola/swift,brentdax/swift,shahmishal/swift,nathawes/swift,hooman/swift,nathawes/swift,jckarter/swift,austinzheng/swift,nathawes/swift,amraboelela/swift,karwa/swift,jckarter/swift,glessard/swift,austinzheng/swift,ahoppen/swift,airspeedswift/swift,apple/swift,jmgc/swift,lorentey/swift,amraboelela/swift,danielmartin/swift,tkremenek/swift,tkremenek/swift,sschiau/swift,shajrawi/swift,harlanhaskins/swift,glessard/swift,danielmartin/swift,natecook1000/swift,xedin/swift,airspeedswift/swift,benlangmuir/swift,danielmartin/swift,shajrawi/swift,parkera/swift,practicalswift/swift