This is a leftover of the previous CL.
https://chromium-review.googlesource.com/c/v8/v8/+/1402305.

noexcept keyword needs to be consistent between the declaration and
implementation in C++17.

Bug: v8:8616, chromium:752720
Change-Id: I8a21426e550d666bd84c1a6e7bc36d1eec495333
Reviewed-on: https://chromium-review.googlesource.com/c/1402305Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58665}