Drive-by-fix: Use switch statement in AsyncHooks::PromiseHookDispatch

Bug: chromium:1239907
Change-Id: I882956bfed92b56e1e8d885bdc68e205dd80c135
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3097882Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76339}