Update missed link to chromium C++11 styleguide

Follow-up to https://webrtc-review.googlesource.com/c/src/+/232260:
there's a second link to the obsolete chromium-cpp.appspot.com in the
same file that was missed.

Also updates the link to be more precise: the new markdown file has
anchors on individual entries, not just the section headers.

R=danilchap@webrtc.org

Bug: chromium:1243839
Change-Id: I17918d155aacf3465a46fd674a598139a0870165
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/232560
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35043}
diff --git a/g3doc/style-guide.md b/g3doc/style-guide.md
index 69f758a..4e6e9a1 100644
--- a/g3doc/style-guide.md
+++ b/g3doc/style-guide.md
@@ -152,7 +152,7 @@
 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-cpp.appspot.com/#library-blocklist
+[chr-std-shared-ptr]: https://chromium.googlesource.com/chromium/src/+/main/styleguide/c++/c++11.md#shared-pointers
 
 ### `std::bind`