[kuwo:song] Correct song ID extraction (fixes #9033)

Bug introduced in daef04a4e7.

youtube_dl/extractor/kuwo.py

@@ -55,7 +55,7 @@ class KuwoBaseIE(InfoExtractor):
 class KuwoIE(KuwoBaseIE):
     IE_NAME = 'kuwo:song'
     IE_DESC = '酷我音乐'
-    _VALID_URL = r'https?://www\.kuwo\.cn/yinyue/(?P<id>\d+?)'
+    _VALID_URL = r'https?://www\.kuwo\.cn/yinyue/(?P<id>\d+)'
     _TESTS = [{
         'url': 'http://www.kuwo.cn/yinyue/635632/',
         'info_dict': {