MD Settings: Add missing month from credit card month dropdown.

BUG=632761
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2198443003
Cr-Commit-Position: refs/heads/master@{#408780}

chrome/browser/resources/settings/passwords_and_forms_page/credit_card_edit_dialog.js

@@ -34,7 +34,7 @@ Polymer({
     monthList_: {
       type: Array,
       value: [
-        '01', '02', '03', '04', '05', '06', '07', '09', '10', '11', '12',
+        '01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11', '12',
       ],
     },