[twitter] remove 'date_liked' (#3850, #4108, #4657)

Twitter's 'sortIndex' can't be used to calculate the timestamp
of when a Tweet was liked anymore.

gallery_dl/extractor/twitter.py

@@ -603,12 +603,6 @@ class TwitterLikesExtractor(TwitterExtractor):
     def tweets(self):
         return self.api.user_likes(self.user)
 
-    def _transform_tweet(self, tweet):
-        tdata = TwitterExtractor._transform_tweet(self, tweet)
-        tdata["date_liked"] = text.parse_timestamp(
-            (int(tweet["sortIndex"] or 0) >> 20) // 1000)
-        return tdata
-
 
 class TwitterBookmarkExtractor(TwitterExtractor):
     """Extractor for bookmarked tweets"""