Adapt SNAPSHOT plugin api example to the 3.1 version

Change-Id: I9244781436f3ae11aee9ea6a77b5030f5d72b7f7

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 23f2792..85f76dd 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -16,4 +16,4 @@
 gerrit_api()
 
 # Load snapshot Plugin API
-#gerrit_api(version = "3.0.xy-SNAPSHOT")
+#gerrit_api(version = "3.1.xy-SNAPSHOT")