[youtube] Fix extraction of age gate videos (closes #3270)

Setting the correct value of the 'sts' paramater in the 'get_video_info' url gives the correct urls.
Removed parameters that are not needed.

youtube_dl/extractor/youtube.py

@@ -609,13 +609,10 @@ class YoutubeIE(YoutubeBaseInfoExtractor, SubtitlesInfoExtractor):
             age_gate = True
             # We simulate the access to the video from www.youtube.com/v/{video_id}
             # this can be viewed without login into Youtube
-            data = compat_urllib_parse.urlencode({'video_id': video_id,
-                                                  'el': 'player_embedded',
-                                                  'gl': 'US',
-                                                  'hl': 'en',
+            data = compat_urllib_parse.urlencode({
+                'video_id': video_id,
                 'eurl': 'https://youtube.googleapis.com/v/' + video_id,
-                                                  'asv': 3,
-                                                  'sts':'1588',
+                'sts':'16268',
             })
             video_info_url = proto + '://www.youtube.com/get_video_info?' + data
             video_info_webpage = self._download_webpage(video_info_url, video_id,