Checked Span: Enable in release

We fully expect this to get reverted, perhaps automatically, and that's
all right. This CL is intended to show the viability (or the major sharp
edges) of Checked Span in a canary / dev release of Chrome.

Change-Id: Ice22e05e5bf050dc09b1eeb1f3b8226ba1c75dbe
Bug: 501113358
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7624900
Auto-Submit: Kalvin Lee <kdlee@chromium.org>
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Commit-Queue: Stephen Nusko <nuskos@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1617375}
NOKEYCHECK=True
GitOrigin-RevId: 41af5c65823240f0a1510b3d9e9990d0c1e03252