[Privacy Sandbox] Update Histogram

Histogram needed for privacy sandbox expired, unexpire the histogram
with a note about its missing data in the expired window.

Change-Id: Ie048f7fd9368ee8fdf96f047fcdb03a112e0b178
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3382817


Reviewed-by: Theodore Olsauskas-Warren <sauski@google.com>
Commit-Queue: Sean Harrison <harrisonsean@chromium.org>
Cr-Commit-Position: refs/heads/main@{#958030}