Fixes brave/brave-browser#34636 Related Chromium commit: https://source.chromium.org/chromium/chromium/src/+/84ed1f62ecd64bbfc3d2c4775a6e80a6b0e9defb Clean up SendTabToSelfSigninPromo flag Enabled by default in M119 (https://crrev.com/c/4905024), can be cleaned up in M120. Fixed: 1479693, 1295204 Change-Id: Ic778e9c886a5d9391fb5da7510d166952481fe21 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4905343 Reviewed-by: Boris Sazonov <bsazonov@chromium.org> Reviewed-by: Wenyu Fu <wenyufu@chromium.org> Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com> Commit-Queue: Victor Vianna <victorvianna@google.com> Cr-Commit-Position: refs/heads/main@{#1204655}