Remove chenleihu@google.com

chenleihu@google.com is leaving Google. Removing the user from
- WATCHLISTS
- OWNERS
- README

Change-Id: Ia821ae9734007aa01b1e3bfa8967a1b82cd81048
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5538792


Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Charlie Hu <chenleihu@google.com>
Cr-Commit-Position: refs/heads/main@{#1300856}