[IPO] Simplify code with DenseMap::operator[] (NFC) (llvm#115261)

Author: kazutakahirata

llvm/lib/Transforms/IPO/Internalize.cpp

@@ -176,7 +176,7 @@ void InternalizePass::checkComdat(
   if (!C)
     return;
 
-  ComdatInfo &Info = ComdatMap.try_emplace(C).first->second;
+  ComdatInfo &Info = ComdatMap[C];
   ++Info.Size;
   if (shouldPreserveGV(GV))
     Info.External = true;