Update owner + expiry of Prefetch Proxy histograms

This CL updates the prefetch proxy histogram owner to the current owner,
and alignes the expiry of them to 2024-09-01.

Bug: 329089003, 329088962, 329088941, 329088847, 329088700, 329088351, 329088589, 329088231, 329089076, 329088183
Change-Id: I93407313ecc379e3c81750a2861606d3e30064fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5465002
Reviewed-by: Liviu Tinta <liviutinta@chromium.org>
Reviewed-by: Simon Pelchat <spelchat@chromium.org>
Commit-Queue: Kouhei Ueno <kouhei@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1291099}