Fix typo in OptimizationTips.rst
Fix typo in OptimizationTips.rst

d is assigned to d, not the other way around
hooman/swift,atrick/swift,tkremenek/swift,tkremenek/swift,JGiola/swift,gregomni/swift,apple/swift,parkera/swift,gregomni/swift,ahoppen/swift,atrick/swift,tkremenek/swift,ahoppen/swift,xwu/swift,parkera/swift,rudkx/swift,glessard/swift,xwu/swift,tkremenek/swift,apple/swift,tkremenek/swift,parkera/swift,benlangmuir/swift,glessard/swift,tkremenek/swift,benlangmuir/swift,xwu/swift,roambotics/swift,glessard/swift,ahoppen/swift,ahoppen/swift,xwu/swift,glessard/swift,xwu/swift,hooman/swift,roambotics/swift,hooman/swift,apple/swift,rudkx/swift,benlangmuir/swift,apple/swift,ahoppen/swift,rudkx/swift,hooman/swift,tkremenek/swift,atrick/swift,parkera/swift,JGiola/swift,hooman/swift,glessard/swift,roambotics/swift,roambotics/swift,roambotics/swift,apple/swift,parkera/swift,gregomni/swift,roambotics/swift,JGiola/swift,parkera/swift,hooman/swift,gregomni/swift,glessard/swift,atrick/swift,apple/swift,parkera/swift,rudkx/swift,ahoppen/swift,benlangmuir/swift,xwu/swift,atrick/swift,gregomni/swift,rudkx/swift,JGiola/swift,benlangmuir/swift,gregomni/swift,atrick/swift,hooman/swift,parkera/swift,xwu/swift,benlangmuir/swift,JGiola/swift,JGiola/swift,rudkx/swift