Fix Picker tests to make them independent of Picker flags.

This ensures the tests pass regardless of which flags are enabled.

Bug: b/339712718
Change-Id: I20295ef979336eb4e468357ff04a8e726260680c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5526383
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: David Padlipsky <dpad@google.com>
Auto-Submit: Darren Shen <shend@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1299313}