libunwindstack: Set update mechanism This CL sets the Update Mechanism to Manual. [email protected] Bug: 445311061 Change-Id: I3b5cce4ced8d01b91c8bc3ede826325d384e86df Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/third_party/libunwindstack/+/7509829 Reviewed-by: Jiewei Qian <[email protected]> Owners-Override: Jordan Brown <[email protected]> Reviewed-by: Patrick Meiring <[email protected]>