[omnibox] Enable default browser pedal by default

This low-risk feature is planned for natural rollout with killswitch.

Bug: 1383484
Change-Id: I02499f66dc2e9a3e4eb714ccd559a190a67b637a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4348485


Reviewed-by: manuk hovanesian <manukh@chromium.org>
Commit-Queue: Orin Jaworski <orinj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118895}