Refresh WebRTC style guide

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}
diff --git a/g3doc/style-guide.md b/g3doc/style-guide.md
index 63ca7d9..5a2487c 100644
--- a/g3doc/style-guide.md
+++ b/g3doc/style-guide.md
@@ -1,16 +1,12 @@
 # WebRTC coding style guide
 
 <?% config.freshness.owner = 'danilchap' %?>
-<?% config.freshness.reviewed = '2021-05-12' %?>
+<?% config.freshness.reviewed = '2022-01-17' %?>
 
 ## General advice
 
 Some older parts of the code violate the style guide in various ways.
-
-* If making small changes to such code, follow the style guide when it's
-  reasonable to do so, but in matters of formatting etc., it is often better to
-  be consistent with the surrounding code.
-* If making large changes to such code, consider first cleaning it up in a
+If making large changes to such code, consider first cleaning it up in a
   separate CL.
 
 ## C++
@@ -141,9 +137,7 @@
    * `rtc::scoped_refptr` for all objects with shared ownership
 
 Use of `std::shared_ptr` is *not permitted*. It is banned in the Chromium style
-guide (overriding the Google style guide), and offers no compelling advantage
-over `rtc::scoped_refptr` (which is cloned from the corresponding Chromium
-type). See the
+guide (overriding the Google style guide). See the
 [list of banned C++ library features in Chromium][chr-std-shared-ptr] for more
 information.
 
@@ -152,7 +146,7 @@
 exist both from the API users and internally, with no way to invalidate pointers
 held by the API user, `rtc::scoped_refptr` can be appropriate.
 
-[chr-std-shared-ptr]: https://chromium.googlesource.com/chromium/src/+/main/styleguide/c++/c++11.md#shared-pointers
+[chr-std-shared-ptr]: https://chromium.googlesource.com/chromium/src/+/main/styleguide/c++/c++11.md#shared-pointers-banned
 
 ### `std::bind`
 
@@ -180,11 +174,8 @@
 There's a substantial chunk of legacy C code in WebRTC, and a lot of it is old
 enough that it violates the parts of the C++ style guide that also applies to C
 (naming etc.) for the simple reason that it pre-dates the use of the current C++
-style guide for this code base.
-
-* If making small changes to C code, mimic the style of the surrounding code.
-* If making large changes to C code, consider converting the whole thing to C++
-  first.
+style guide for this code base. If making large changes to C code, consider
+converting the whole thing to C++ first.
 
 ## Java