This commit removes the explicit namespace in FunctionCallbackArguments
constructor. They are not needed and this change seems to be consistent
with other CustomArguments classes like PropertyCallbackArguments.

Change-Id: If18371fbb2e6a7161ea4a1633f4219f3498cdc8c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2141740Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67148}