Fix Gerrit version we use in README

At the moment we use the 3.0.3 release.

Change-Id: Ic4ef9ef4aaa3ae38e7f1fae758a9a3018ccf28fb
diff --git a/README.md b/README.md
index 2aebbea..0d57798 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 
 # Docker images
 
-Images to run a Gerrit master and slave setup based on the latest stable-2.12 Gerrit build.
+Images to run a Gerrit master and slave setup based on the 3.0.3 Gerrit release.
 
 ## Building images