[mlir] Use a range constructor of DenseSet (NFC) (llvm#133355)

Author: kazutakahirata

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -882,9 +882,8 @@ static LogicalResult verifyOutputShape(
     lhsContractingDimSet.insert(dimPair.first);
     rhsContractingDimSet.insert(dimPair.second);
   }
-  DenseSet<int64_t> rhsBatchDimSet;
-  for (auto &dimPair : batchDimMap)
-    rhsBatchDimSet.insert(dimPair.second);
+  DenseSet<int64_t> rhsBatchDimSet(llvm::from_range,
+                                   llvm::make_second_range(batchDimMap));
 
   // Add free and batch dimensions from 'lhsType' to 'expectedResultDims'.
   SmallVector<int64_t, 4> expectedResultDims;