[EasyUnlock] Fix HTML typo in turn off dialog UI.

BUG=751783

Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ifefe73dbc4039201f32fef25fa48f04541d6af20
Reviewed-on: https://chromium-review.googlesource.com/598436Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Reviewed-by: Gustavo Sacomoto <sacomoto@chromium.org>
Commit-Queue: Tim Song <tengs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491524}

chrome/browser/resources/settings/people_page/easy_unlock_turn_off_dialog.html

@@ -17,7 +17,7 @@
       <div slot="body">
         [[getDescriptionText_(status_)]]
       </div>
-      <div slot="button-container">
+      <div slot="button-container"
           hidden="[[isButtonBarHidden_(status_)]]">
         <paper-spinner active="[[isSpinnerActive_(status_)]]">
         </paper-spinner>