[NFC] Fix comment describing what EdgeBundles is

[mkazantsev]

Summary

The original comment says the same thing twice, and does not mention that
edges entering the block are also in the same bundle (which seems true from
what the underlying code is doing).

[mkazantsev]

Just a sanity check that I understood it correctly.

[reames]

Never looked at this code, not a qualified reviewer.

[RKSimon]

Makes sense to me, but I don't think anyone other than @stoklund ever touched this code other than for general maintenance work.

llvm/include/llvm/CodeGen/EdgeBundles.h

 //===-------- EdgeBundles.h - Bundles of CFG edges --------------*- c++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // The EdgeBundles analysis forms equivalence classes of CFG edges such that all
 // edges leaving a machine basic block are in the same bundle, and all edges
-// leaving a basic block are in the same bundle.
+// entering a machine basic block are in the same bundle.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CODEGEN_EDGEBUNDLES_H
 #define LLVM_CODEGEN_EDGEBUNDLES_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/IntEqClasses.h"