When comparing two-byte strings, the correct number of characters to
compare is length(), not byte_length().

The bug was introduced in
https://chromium-review.googlesource.com/c/v8/v8/+/2533038

There's no regression test, since going beyond the AstRawString
boundary generally doesn't crash.

Bug: chromium:1151602
Change-Id: I32c297c2751835dd7574ff928d2d5b8346b4381a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2551110Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71330}