Fixing presubmit

Exact reason this started failing spontaneously is unclear. However,
the failing behavior is transitional anyway and will be removed once the
Travel app is fully integrated with Syncbase watch, and the last set of
changes I made to the mock made the 'memory' flag on the update even
unwarranted anyway.

Change-Id: Ife3e84ccc3553a88a1523a64c5a067f7a052d8f2
diff --git a/browser/mocks/syncbase-wrapper.js b/browser/mocks/syncbase-wrapper.js
index d65dace..d6afd33 100644
--- a/browser/mocks/syncbase-wrapper.js
+++ b/browser/mocks/syncbase-wrapper.js
@@ -365,7 +365,7 @@
   // TODO(rosswang): transitional
   events: {
     onError: 'memory',
-    onUpdate: 'memory'
+    onUpdate: ''
   },
   // TODO(rosswang): end transitional