[bambuser] remove extractor

https://web.archive.org/web/20190808014227/https://go.bambuser.com/shutdown-announcement

youtube_dl/extractor/extractors.py

@@ -80,7 +80,6 @@ from .awaan import (
 )
 from .azmedien import AZMedienIE
 from .baidu import BaiduVideoIE
-from .bambuser import BambuserIE, BambuserChannelIE
 from .bandcamp import BandcampIE, BandcampAlbumIE, BandcampWeeklyIE
 from .bbc import (
     BBCCoUkIE,