Set Gerrit to 3.13.1

Change-Id: I1987dc3520ec932440af00b3e0cd302d342522ea
diff --git a/Version.mk b/Version.mk
index 228117e..fc2596a 100644
--- a/Version.mk
+++ b/Version.mk
@@ -1,4 +1,4 @@
-VERSION=3.13.0
-WAR_VERSION=3.13.0
+VERSION=3.13.1
+WAR_VERSION=3.13.1
 BRANCH=stable-3.13
 RELEASE=1