The immediates would have been checked by the validation, so we can skip
masking them.

Bug: v8:10696
Change-Id: I18e4746b1eb08a2436311a633341be0c88f52139
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2453456
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70394}