Docs: mention [email protected] in adding_to_third_party.md

The email is already mentioned in docs/security/sheriff.md but
it's good to have it mentioned in the docs about adding
a third party dependency.

Change-Id: I04e9d4751ca849cd96718081f9fe7d233905dbb8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3483802
Reviewed-by: Daniel Cheng <[email protected]>
Commit-Queue: Alex Rudenko <[email protected]>
Cr-Commit-Position: refs/heads/main@{#974238}
diff --git a/docs/adding_to_third_party.md b/docs/adding_to_third_party.md
index 39ed172..8128306 100644
--- a/docs/adding_to_third_party.md
+++ b/docs/adding_to_third_party.md
@@ -186,8 +186,9 @@
 
 * Make sure you have the approval from Chrome Eng Review as mentioned
   [above](#before-you-start).
-* Get [email protected] approval. Email the list with relevant details and
-  a link to the CL. Third party code is a hot spot for security vulnerabilities.
+* Get [email protected] (or [email protected], Google-only)
+  approval. Email the list with relevant details and a link to the CL.
+  Third party code is a hot spot for security vulnerabilities.
   When adding a new package that could potentially carry security risk, make
   sure to highlight risk to [email protected]. You may be asked to add
   a README.security or, in dangerous cases, README.SECURITY.URGENTLY file.