Remove advice to keep legacy style for consistency because it condridicts a recent addition to style guide goals Remove debatable reason for banning std::shared_ptr, keep main reason to ban it as the only one. Bug: None Change-Id: I4c31f9247a33430df0b286a15f1a35ab23060d1c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/247183 Reviewed-by: Artem Titov <titovartem@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/main@{#35720}