[InlineCost] Remove a dead constant; NFC

My `grep`-fu indicates that this hasn't been used for years. It also no
longer makes much sense to have this flavor of penalty in general, since
a call to a noreturn should mean that we're in a BB that's terminated by
`unreachable`. That case is accounted for by
CallAnalyzer::allowSizeGrowth.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@345789 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/InlineCost.h

@@ -46,7 +46,6 @@ const int IndirectCallThreshold = 100;
 const int CallPenalty = 25;
 const int LastCallToStaticBonus = 15000;
 const int ColdccPenalty = 2000;
-const int NoreturnPenalty = 10000;
 /// Do not inline functions which allocate this many bytes on the stack
 /// when the caller is recursive.
 const unsigned TotalAllocaSizeRecursiveCaller = 1024;