Revert "Bump yang tools version to 2.4"

This reverts commit 5193cb736c41d52f6007e7e2bdfd619b7598604f.

Change-Id: If061ca507f702f161fa112188abd26aa4924618d
diff --git a/lib/deps.json b/lib/deps.json
index ede7521..223f4e71 100644
--- a/lib/deps.json
+++ b/lib/deps.json
@@ -247,13 +247,13 @@
     "aries-util": "mvn:org.apache.aries:org.apache.aries.util:1.1.1",
     "guava20": "mvn:com.google.guava:guava:20.0",
 
-    // Note update BVER in tools/dev/bin/patch-yang-libs and YANG_VER in tools/build/onos-buck
-    "onos-yang-model":"mvn:org.onosproject:onos-yang-model:2.4.1",
-    "onos-yang-compiler-api":"mvn:org.onosproject:onos-yang-compiler-api:2.4.1",
-    "onos-yang-runtime":"mvn:org.onosproject:onos-yang-runtime:2.4.1",
-    "onos-yang-serializers-json":"mvn:org.onosproject:onos-yang-serializers-json:2.4.1",
-    "onos-yang-serializers-xml":"mvn:org.onosproject:onos-yang-serializers-xml:2.4.1",
-    "onos-yang-serializers-utils":"mvn:org.onosproject:onos-yang-serializers-utils:2.4.1",
+    // Note: update BVER in tools/dev/bin/patch-yang-libs
+    "onos-yang-model":"mvn:org.onosproject:onos-yang-model:2.3.1",
+    "onos-yang-compiler-api":"mvn:org.onosproject:onos-yang-compiler-api:2.3.1",
+    "onos-yang-runtime":"mvn:org.onosproject:onos-yang-runtime:2.3.1",
+    "onos-yang-serializers-json":"mvn:org.onosproject:onos-yang-serializers-json:2.3.1",
+    "onos-yang-serializers-xml":"mvn:org.onosproject:onos-yang-serializers-xml:2.3.1",
+    "onos-yang-serializers-utils":"mvn:org.onosproject:onos-yang-serializers-utils:2.3.1",
     "org.apache.servicemix.bundles.dom4j":"mvn:org.apache.servicemix.bundles:org.apache.servicemix.bundles.dom4j:1.6.1_5",
     "plexus-utils": "mvn:org.codehaus.plexus:plexus-utils:3.0.24",
     "sshd-core": "mvn:org.apache.sshd:sshd-core:1.4.0",