It was on JSGlobalProxyRef but in reality the property cells exist in
the global object, not in the global proxy.

Bug: v8:7790
Change-Id: Ia7bd5731c730db09602a1aec61b64b1355abf6a0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1841352
Commit-Queue: Georg Neis <neis@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64112}