Update for a recent spec change: https://github.com/WebAssembly/reference-types/pull/38

R=binji@chromium.org

Bug: v8:7581
Change-Id: I4ac4a4c351dfc100f978e1aead308cbed59149e4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1690832Reviewed-by: Ben Smith <binji@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62576}