download.js: remove document.querySelectorAll polyfill (#2601)

Such browsers won't work anyway.

static/js/download.js

@@ -1,32 +1,6 @@
-;
-(function (d, n) {
+;(function (d, n) {
   'use strict'
 
-  // document.querySelectorAll polyfill for ancient IEs
-  // https://gist.github.com/chrisjlee/8960575
-  if (!document.querySelectorAll) {
-    document.querySelectorAll = function (selectors) {
-      var style = document.createElement('style')
-      var elements = []
-      var element
-
-      document.documentElement.firstChild.appendChild(style)
-      document._qsa = []
-
-      style.styleSheet.cssText = selectors + '{x-qsa:expression(document._qsa && document._qsa.push(this))}'
-      window.scrollBy(0, 0)
-      style.parentNode.removeChild(style)
-
-      while (document._qsa.length) {
-        element = document._qsa.shift()
-        element.style.removeAttribute('x-qsa')
-        elements.push(element)
-      }
-      document._qsa = null
-      return elements
-    }
-  }
-
   var osMatch = n.platform.match(/(Win|Mac|Linux)/)
   var os = (osMatch && osMatch[1]) || ''
   var arch = n.userAgent.match(/x86_64|Win64|WOW64/) ||