dms: no need to remove <base> in PDF viewer

I'm not sure what was the problem from this comment, but we render
the gadget in an iframe so there's no need to change the DOM like this.
Probably this was a problem in early versions when it was in the same
page.

bt5/erp5_dms/SkinTemplateItem/portal_skins/erp5_dms/pdf_js/pdf.gadget.js.js

@@ -13,13 +13,6 @@
         });
     })
     .declareMethod("render", function (options) {
-      [].forEach.call(window.document.head.querySelectorAll("base"), function (el) {
-        // XXX GadgetField adds <base> tag to fit to the parent page location, it's BAD to remove them.
-        //     In the case of pdf.js, all component are loaded dynamicaly through ajax requests in
-        //     pdf-js "folder". By setting a <base> tag, we change the url resolution behavior, and
-        //     we break all dynamic links. So, deleting <base> is required.
-        window.document.head.removeChild(el);
-      });
       this.props.key = options.key;
       webViewerLoad(options.value);