The flags were added because scalar lowering was not implemented for the
instructions in the test. Now that scalar lowering is complete, we can
remove these flags.

Fixed: v8:11137
Change-Id: Ic7bdedbfe558fafebe98917fe4e6a7922203ba91
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2565078Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71474}