Update latest LTS version to 1.4.0 (#104)

Co-authored-by: andrew <laxmaxer@gmail.com>

latest-iotedge-lts.json

@@ -1,5 +1,5 @@
 {
-    "iotedged": "1.1.15",
-    "azureiotedge-agent": "1.1.15",
-    "azureiotedge-hub": "1.1.15"
-}
+    "iotedged": "1.4.0",
+    "azureiotedge-agent": "1.4.0",
+    "azureiotedge-hub": "1.4.0"
+}