Set Gerrit to 3.1.5

Change-Id: Ie135253195ba65df1341c82612549d60f5944065
diff --git a/common.env b/common.env
index 6567028..d078757 100644
--- a/common.env
+++ b/common.env
@@ -5,7 +5,7 @@
 
 # Gerrit version
 GERRIT_VERSION=3.1
-GERRIT_PATCH=4
+GERRIT_PATCH=5
 GERRIT_BRANCH=stable-$(GERRIT_VERSION)
 
 # Gerrit CI