Fix typo in docs. (html5lib#300)

Statement was repeated twice on a single line.

doc/movingparts.rst

@@ -136,7 +136,7 @@ To use a filter, simply wrap it around a stream:
  >>> dom = html5lib.parse("<p><script>alert('Boo!')", treebuilder="dom")
  >>> walker = html5lib.getTreeWalker("dom")
  >>> stream = walker(dom)
- >>> sane_stream = sanitizer.Filter(stream) clean_stream = sanitizer.Filter(stream)
+ >>> clean_stream = sanitizer.Filter(stream)
 
 
 Tree adapters