[InfoExtractor] Use kwarg maxsplit for re.split

* May become kw-only in future Pythons

youtube_dl/extractor/common.py

@@ -3170,7 +3170,7 @@ class InfoExtractor(object):
                     # See com/longtailvideo/jwplayer/media/RTMPMediaProvider.as
                     # of jwplayer.flash.swf
                     rtmp_url_parts = re.split(
-                        r'((?:mp4|mp3|flv):)', source_url, 1)
+                        r'((?:mp4|mp3|flv):)', source_url, maxsplit=1)
                     if len(rtmp_url_parts) == 3:
                         rtmp_url, prefix, play_path = rtmp_url_parts
                         a_format.update({