Relinquish disk space in fuzz coverage collection.

This job was failing due to excessive disk space usage. This should
result in space usage matching, or being less than, before
https://crrev.com/1432992775c8b25fd623379ea6d605927b18cb3d

Bug: 1498406
Change-Id: I17b1068901b2552a4b6c9633a40580f248eb42c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5033735
Commit-Queue: Adrian Taylor <adetaylor@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Auto-Submit: Adrian Taylor <adetaylor@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1225864}
NOKEYCHECK=True
GitOrigin-RevId: 3bd72435ec79f35d934222806ea43f3f1308bd41