Update recommended TODO format to latest recommendations

Recommended TODO format was recently reviewed once again and mostly
reverted to pre-2023 format.

Update sample with longer issue id to encourage post-monorail migration
numbers over shorter pre-migrations number

Bug: None
No-Try: True
Change-Id: I1f2f869db86bfcce47e9c5f2c00140078ab6acd1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/487760
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48164}

g3doc/style-guide.md

diff --git a/g3doc/style-guide.md b/g3doc/style-guide.md
index 3f72072..88ebb2c 100644
--- a/g3doc/style-guide.md
+++ b/g3doc/style-guide.md
@@ -57,11 +57,13 @@
 
 ### `TODO` comments
 
-Follow the [Google styleguide for `TODO` comments][goog-style-todo]. When
-referencing a WebRTC bug, prefer using the URL form (excluding the scheme part):
+Follow the [Google styleguide for `TODO` comments][goog-style-todo]. TODOs
+should have a syntax of the following form `TODO(<metadata,...>): <content>`
+When referencing a WebRTC bug, prefer using the URL form (excluding the scheme
+part):
 
 ```cpp
-// TODO: bugs.webrtc.org/12345 - Delete the hack when blocking bugs are resolved.
+// TODO(bugs.webrtc.org/42224904): Delete when blocking bugs are resolved.
 ```
 
 The short form used in commit messages, e.g. `webrtc:12345`, is discouraged.