Remove redundant DWC in BrowserContextImpl

NOTREACHED() currently uploads using DumpWithoutCrashing so we get
duplicate reports for all of these.

Bug: 1423567
Change-Id: I9953c10772a0c7aba5ffee0c4c8b57a2aa5eb96e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4345488


Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Auto-Submit: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118223}