Avoid u8"", just use "".

In C++20, u8"" generates a const char8_t*, not a const char*.  Since ""
accepts UTF-8 already, just switch to it.

Bug: chromium:1284275
Change-Id: I873321a62a4d9e32b3b463913a3bc10231db3db3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3630347Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80382}