[iOS] Adds isContextMenuActionsRefreshEnabled to EG2

This CL adds isContextMenuActionsRefreshEnabled to EG2 in order to test
the ContextMenuActionsRefresh feature.

Bug: 1241012
Change-Id: I91deff0178bba1b73ad872ce149ba9a12b32c2bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3122596


Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#915933}