Upgrade yt_dlp and download script

plugins/youtube_download/yt_dlp/extractor/ku6.py

@@ -10,7 +10,7 @@ class Ku6IE(InfoExtractor):
             'id': 'JG-8yS14xzBr4bCn1pu0xw',
             'ext': 'f4v',
             'title': 'techniques test',
-        }
+        },
     }
 
     def _real_extract(self, url):
@@ -19,12 +19,12 @@ class Ku6IE(InfoExtractor):
 
         title = self._html_search_regex(
             r'<h1 title=.*>(.*?)</h1>', webpage, 'title')
-        dataUrl = 'http://v.ku6.com/fetchVideo4Player/%s.html' % video_id
-        jsonData = self._download_json(dataUrl, video_id)
-        downloadUrl = jsonData['data']['f']
+        data_url = f'http://v.ku6.com/fetchVideo4Player/{video_id}.html'
+        json_data = self._download_json(data_url, video_id)
+        download_url = json_data['data']['f']
 
         return {
             'id': video_id,
             'title': title,
-            'url': downloadUrl
+            'url': download_url,
         }