Fix typo in SLPVectorizer.cpp

[ArchDRobison]

Summary

When some logic in SLPVectorizer was extended from pairs to lists, the word "pair" in a debug message was not likewise changed. This patch changes the word from "pair" to "list".

[ArchDRobison]

Updated to include another typo. Should the two typos be in separate patches?

[nadav]

One patch is okay. The patch LGTM.

SLPVectorizer.cpp

   if (!isPowerOf2_32(Sz) || VF < 2)
     return false;
 
-  // Keep track of values that were delete by vectorizing in the loop below.
+  // Keep track of values that were deleted by vectorizing in the loop below.
   SmallVector<WeakVH, 8> TrackValues(Chain.begin(), Chain.end());
 
   bool Changed = false;

     int Cost = R.getTreeCost();
 
     if (Cost < -SLPCostThreshold) {
-      DEBUG(dbgs() << "SLP: Vectorizing pair at cost:" << Cost << ".\n");
+      DEBUG(dbgs() << "SLP: Vectorizing list at cost:" << Cost << ".\n");
       R.vectorizeTree();
 
       // Move to the next bundle.