Remove schenney@chromium.org from third_party/libxml/OWNERS.

This suggested change is automatically generated based on group memberships and affiliations.
If this change is unnecessary or in error, vote CR -1 and the bot will abandon it. Vote CR +1/2 to approve this change.
See the owner's recent activity for context: https://chromium-review.googlesource.com/q/schenney@chromium.org

To report an issue, file a bug in the Infra>Security component.

Change-Id: I9b542979116875f80a3194ecd9837913b0addf10
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4392053
Auto-Submit: Owners Cleanup <swarming-tasks@owners-cleanup-prod.google.com.iam.gserviceaccount.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1125173}
NOKEYCHECK=True
GitOrigin-RevId: 15aaf1596b054e0547c8a34b292482112c019bc6