tests: Rename close function in window_open.html

Naming it close() conflicts with the global JS close()

tests/end2end/data/javascript/window_open.html

@@ -17,7 +17,7 @@
         window.open('', 'my_window');
     }
 
-    function close() {
+    function close_normal() {
         my_window.close();
     }
 
@@ -33,7 +33,7 @@
 <button onclick="open_normal()" id="open-normal">normal</button>
 <button onclick="open_modal()" id="open-modal">modal</button>
 <button onclick="open_invalid()" id="open-invalid">invalid/no URL</button>
-<button onclick="close()" id="close-normal">close</button>
+<button onclick="close_normal()" id="close-normal">close</button>
 <button onclick="close_twice()" id="close-twice">close twice (issue 906)</button>
 
 </body>