Remove obsolete seccomp_unwinder for legacy (pre-BPF) sandbox

src/client/linux/dump_writer_common/seccomp_unwinder.h

-// Copyright (c) 2014, Google Inc.
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#ifndef CLIENT_LINUX_DUMP_WRITER_COMMON_SECCOMP_UNWINDER_H
-#define CLIENT_LINUX_DUMP_WRITER_COMMON_SECCOMP_UNWINDER_H
-
-#include "client/linux/dump_writer_common/raw_context_cpu.h"
-#include "google_breakpad/common/minidump_format.h"
-
-namespace google_breakpad {
-
-struct SeccompUnwinder {
-
-  // Check if the top of the stack is part of a system call that has been
-  // redirected by the seccomp sandbox. If so, try to pop the stack frames
-  // all the way back to the point where the interception happened.
-  static void PopSeccompStackFrame(RawContextCPU* cpu,
-                                   const MDRawThread& thread,
-                                   uint8_t* stack_copy);
-};
-
-}  // namespace google_breakpad
-
-#endif  // CLIENT_LINUX_DUMP_WRITER_COMMON_SECCOMP_UNWINDER_H