fix e2e test

e2e/ambassador/src/background/index.js

@@ -1,6 +1,6 @@
 import {
   WINDOWS_CREATE, WINDOWS_REMOVE, WINDOWS_GET,
-  TABS_CREATE, TABS_REMOVE, TABS_SELECT_AT, TABS_GET_ZOOM, TABS_SET_ZOOM,
+  TABS_CREATE, TABS_SELECT_AT, TABS_GET_ZOOM, TABS_SET_ZOOM,
   EVENT_KEYPRESS, EVENT_KEYDOWN, EVENT_KEYUP,
   SCROLL_GET, SCROLL_SET,
 } from '../shared/messages';
@@ -20,8 +20,6 @@ receiveContentMessage((message) => {
       url: message.url,
       windowId: message.windowId,
     });
-  case TABS_REMOVE:
-    return browser.tabs.remove(message.tabId);
   case TABS_SELECT_AT:
     return tabs.selectAt({
       windowId: message.windowId,