[vk.com] Updated the description to include vk.com.

youtube_dl/extractor/vk.py

@@ -208,7 +208,7 @@ class VKIE(InfoExtractor):
 
 class VKUserVideosIE(InfoExtractor):
     IE_NAME = 'vk.com:user-videos'
-    IE_DESC = 'All of a user\'s videos'
+    IE_DESC = 'vk.com:All of a user\'s videos'
     _VALID_URL = r'https?://(?:m\.)?vk\.com/videos([0-9]+)(?:m\?.*)?'
     _TEMPLATE_URL = 'https://vk.com/videos'
     _TEST = {