[Test] Duplicate test/TypeDecoder/existentials.swift with explicit existential types enabled.
[Test] Duplicate test/TypeDecoder/existentials.swift with explicit
existential types enabled.

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