[mlir][vector][NFC] Clean up vector gather lowering comments

[kuhar]

Summary

These got relocated recently.

mlir/include/mlir/Dialect/Vector/Transforms/LoweringPatterns.h

 /// vector.extract_strided_slice.
 void populateVectorScanLoweringPatterns(RewritePatternSet &patterns,
                                         PatternBenefit benefit = 1);
 
 /// Populate the pattern set with the following patterns:
 ///
 /// [FlattenGather]
 /// Flattens 2 or more dimensional `vector.gather` ops by unrolling the
-/// outermost dimension. For example:
+/// outermost dimension.
 ///
 /// [Gather1DToConditionalLoads]
 /// Turns 1-d `vector.gather` into a scalarized sequence of `vector.loads` or
 /// `tensor.extract`s. To avoid out-of-bounds memory accesses, these
 /// loads/extracts are made conditional using `scf.if` ops.
 void populateVectorGatherLoweringPatterns(RewritePatternSet &patterns,
                                           PatternBenefit benefit = 1);
 

mlir/lib/Dialect/Vector/Transforms/LowerVectorGather.cpp

-//===- LowerVectorScam.cpp - Lower 'vector.scan' operation ----------------===//
+//===- LowerVectorGather.cpp - Lower 'vector.gather' operation ------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements target-independent rewrites and utilities to lower the
-// 'vector.scan' operation.
+// 'vector.gather' operation.
 //
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/Arith/Utils/Utils.h"
 #include "mlir/Dialect/Linalg/IR/Linalg.h"
 #include "mlir/Dialect/MemRef/IR/MemRef.h"