webview: Add bewise as owner to field trials

Because I'm an owner to tools, I get added for reviews to
not-webview-exposed.txt when blink owners are typically trying to launch
web platform features now.

It came up recently where I wanted to block a review until the developer
had updated the field_trials to disable the feature more generally
(crrev.com/c/5117679).
I had to add another webview owner to then approve this file change
which added a bit of churn.

Change-Id: I3a842e7fed68f104cd88adc73e5df197deb69341
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5618671
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Auto-Submit: Rupert Wiser <bewise@chromium.org>
Reviewed-by: Richard (Torne) Coles <torne@chromium.org>
Commit-Queue: Richard (Torne) Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1314148}