bugfix for BrozzlerWorker._needs_browsing

I'm sorry but with my previous commit I introduced a bug in
``BrozzlerWorker._needs_browsing`` method.

More specifically, if the ``brozzler_spy`` param is False (this happens
when ``youtube_dl`` is disabled), ``_needs_browsing`` method returns
always ``False`` and this messes with ``brozzle_page`` workflow. The
browser is nevenr visiting the page.

I'm fixing this here.

brozzler/worker.py

@@ -447,7 +447,9 @@ class BrozzlerWorker:
                 if txn['response_headers'].get_content_type() in [
                         'text/html', 'application/xhtml+xml']:
                     return True
-        return False
+            return False
+        else:
+            return True
 
     def _already_fetched(self, page, brozzler_spy):
         if brozzler_spy: