Fix contributing doc code review description

Change-Id: I134d387f85590afa3dc660f20331e3285fed7b5f

CONTRIBUTING.md

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 6272489..ab993df 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -18,9 +18,9 @@
 ## Code Reviews
 
 All submissions, including submissions by project members, require review. We
-use GitHub pull requests for this purpose. Consult
-[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
-information on using pull requests.
+use Gerrit code review for this purpose. Consult
+[Gerrit User Guide](https://gerrit-documentation.storage.googleapis.com/Documentation/3.8.2/intro-user.html)
+for more information.
 
 ## Community Guidelines