i18n: Remove now-unused ensure_i18n function.

frontend_tests/zjsunit/i18n.js

@@ -18,6 +18,4 @@ i18n.t = function (str, context) {
     return 'translated: ' + str;
 };
 
-i18n.ensure_i18n = function (f) { f(); };
-
 module.exports = i18n;

static/js/translations.js

@@ -20,10 +20,6 @@ i18next
         returnEmptyString: false,  // Empty string is not a valid translation.
     });
 
-i18next.ensure_i18n = function (callback) {
-    callback();
-};
-
 // garbage collect all old-style i18n translation maps in localStorage.
 $(function () {
     if (!localstorage.supported()) {