SmartLock Chrome app: Remove background page from the manifest.

The background page only existed to support BT Classic flow, which is
now gone.

R=tengs@chromium.org

Bug: none
Test: none
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I4af74256299656a119507a209b875a213226fadd
Reviewed-on: https://chromium-review.googlesource.com/964909Reviewed-by: Tim Song <tengs@chromium.org>
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543522}

chrome/browser/resources/easy_unlock/OWNERS

+jhawkins@chromium.org
 tengs@chromium.org
 tbarzic@chromium.org
 

chrome/browser/resources/easy_unlock/manifest.json

@@ -34,12 +34,6 @@
     "systemPrivate"
   ],
 
-  "app": {
-    "background": {
-      "scripts": ["easy_unlock_background.js"]
-    }
-  },
-
   "bluetooth": {
     "socket" : true,
     "low_energy" : true,

chrome/browser/resources/easy_unlock/manifest_signin.json

@@ -25,12 +25,6 @@
     "systemPrivate"
   ],
 
-  "app": {
-    "background": {
-      "scripts": ["easy_unlock_background.js"]
-    }
-  },
-
   "bluetooth": {
     "socket" : true,
     "low_energy" : true,