Making them private was a way to hide the constructor, we can
explicitly delete them, which give a better compilation error message as
well.

Also see: https://stackoverflow.com/q/55205874

Bug: v8:10488
Change-Id: I1c037a501c1da39f027c071e5e64d36fd1c95c6d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2219419Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68049}