Remove files-trash expired unused flag

Bug: 1448604
Change-Id: Icdc36ef2852c7780dcb05171e24c221e470b9210
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4568464


Reviewed-by: Ben Reich <benreich@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1149437}