Removed `WebNavigationNTPDelegate` methods from BVC.

Bug: 1345211
Change-Id: I82b8c5ddb188e3386a6e3d4d714e8474a8e6d588
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3767447


Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Petro Akzhygitov <pakzhygitov@google.com>
Cr-Commit-Position: refs/heads/main@{#1025629}