Update Gerrit in example-setup Dockerfile to 3.12.1

Change-Id: I5eb661b43c1b9856fd3e75d6318cb4c1d2797f4d

example-setup/broker/Dockerfile

diff --git a/example-setup/broker/Dockerfile b/example-setup/broker/Dockerfile
index 9c09461..e9abc46 100644
--- a/example-setup/broker/Dockerfile
+++ b/example-setup/broker/Dockerfile
@@ -1,4 +1,4 @@
-FROM gerritcodereview/gerrit:3.11.4
+FROM gerritcodereview/gerrit:3.12.1
 
 USER root
 

example-setup/http/Dockerfile

diff --git a/example-setup/http/Dockerfile b/example-setup/http/Dockerfile
index 18d88ec..cb4d765 100644
--- a/example-setup/http/Dockerfile
+++ b/example-setup/http/Dockerfile
@@ -1,4 +1,4 @@
-FROM gerritcodereview/gerrit:3.11.4
+FROM gerritcodereview/gerrit:3.12.1
 
 USER root