[SILInliner] NFC: Clarified conditional.
[SILInliner] NFC: Clarified conditional.

Made it clear that one code path was to be followed if
-enable-experimental-lexical-lifetimes was passed and an entirely
different one was to be followed otherwise.

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