[NFC][DSE] Fix typo comment in eliminateDeadStores (#75166)

> We are re-using tryToMergePartialOverlappingStores, which requires
DeadSI to dominate DeadSI.

Should be "DeadSI to dominate KillingSI" because that's what the check
is for.

Author: omern1

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -2170,7 +2170,7 @@ static bool eliminateDeadStores(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
           auto *DeadSI = dyn_cast<StoreInst>(DeadI);
           auto *KillingSI = dyn_cast<StoreInst>(KillingI);
           // We are re-using tryToMergePartialOverlappingStores, which requires
-          // DeadSI to dominate DeadSI.
+          // DeadSI to dominate KillingSI.
           // TODO: implement tryToMergeParialOverlappingStores using MemorySSA.
           if (DeadSI && KillingSI && DT.dominates(DeadSI, KillingSI)) {
             if (Constant *Merged = tryToMergePartialOverlappingStores(