Disable storage3 check in NewStringAppending
Disable storage3 check in NewStringAppending

The other instances had been disabled in commit 5236224eb16a.
FileCheck was recently updated so that it complains about undefined
variables, which is why no one noticed until now. storage3 wasn't
defined because the place where it got defined was disabled. Disabling
that instance now.

glessard/swift,apple/swift,roambotics/swift,gregomni/swift,glessard/swift,atrick/swift,rudkx/swift,benlangmuir/swift,xwu/swift,benlangmuir/swift,roambotics/swift,JGiola/swift,apple/swift,apple/swift,benlangmuir/swift,benlangmuir/swift,ahoppen/swift,xwu/swift,rudkx/swift,glessard/swift,rudkx/swift,gregomni/swift,gregomni/swift,apple/swift,roambotics/swift,atrick/swift,xwu/swift,ahoppen/swift,ahoppen/swift,ahoppen/swift,ahoppen/swift,JGiola/swift,xwu/swift,ahoppen/swift,rudkx/swift,atrick/swift,roambotics/swift,xwu/swift,atrick/swift,glessard/swift,gregomni/swift,glessard/swift,rudkx/swift,apple/swift,JGiola/swift,benlangmuir/swift,roambotics/swift,apple/swift,JGiola/swift,atrick/swift,gregomni/swift,rudkx/swift,roambotics/swift,xwu/swift,xwu/swift,glessard/swift,atrick/swift,gregomni/swift,JGiola/swift,benlangmuir/swift,JGiola/swift