[intel-mpx] Delete an unnecessary license header

[wallace]

Summary

@labath mentioned to me that test files shouldn't have a license header.
I saw this one some days ago, so I'm doing some cleaning.

lldb/tools/intel-features/intel-mpx/test/main.cpp

-//===-- main.cpp ------------------------------------------------*- 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
-////
-////===----------------------------------------------------------------------===//
-//
-
 const int size = 5;
 
 #include <cstddef>
 #include <cstdlib>
 #include <sys/prctl.h>
 
 void func(int *ptr) {
   int *tmp;