GUI: clean up coding style.

Change-Id: I1dcb036a12896bab88dfe2752c098fe5e8dfc009
diff --git a/web/gui/src/main/webapp/app/onos.css b/web/gui/src/main/webapp/app/onos.css
index 3ed0dd5..b82a6e5 100644
--- a/web/gui/src/main/webapp/app/onos.css
+++ b/web/gui/src/main/webapp/app/onos.css
@@ -67,6 +67,6 @@
     transform: translate(-50%, -50%);
     box-shadow: 2px 2px 24px 5px #888;
     background-color: #eee;
-    margin: 0px;
+    margin: 0;
     padding: 10px;
 }