replace pixel4 with pixel6 in Chrome Health presets

Bug: chromium:1423492

Change-Id: I25ab4002ed07dce00f491a21232ffab65088c26a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4328870
Commit-Queue: Leina Sun <sunxiaodi@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1117628}