[bilibili] Fix video downloading (closes #13001)

youtube_dl/extractor/bilibili.py

@@ -122,6 +122,11 @@ def _real_extract(self, url):
                     'preference': -2 if 'hd.mp4' in backup_url else -3,
                 })
 
+            for a_format in formats:
+                a_format.setdefault('http_headers', {}).update({
+                    'Referer': url,
+                })
+
             self._sort_formats(formats)
 
             entries.append({