CHIPS: Correct remaining usage of clearUsage

CL changes the remaining usage of 'clearUsage' to the appropriate
'clearUnpartitionedUsage' for the site details page.

Bug: 1279760
Change-Id: Ie4bf7b33e82ec8b6fddc4768796c77cf08527dad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3378069


Auto-Submit: Theodore Olsauskas-Warren <sauski@google.com>
Reviewed-by: Sean Harrison <harrisonsean@chromium.org>
Commit-Queue: Theodore Olsauskas-Warren <sauski@google.com>
Cr-Commit-Position: refs/heads/main@{#957167}