Use correct regex escape in doctest

Signed-off-by: Philippe Ombredanne <[email protected]>

src/cluecode/copyrights.py

@@ -4450,7 +4450,7 @@ def remove_code_comment_markers(s):
     Return ``s`` removing code comments such as C and C++ style comment markers and assimilated
 
     >>> remove_code_comment_markers(r"\\*#%; /\\/*a*/b/*c\\d#e%f \\*#%; /")
-    'a b c\\\d e f'
+    'a b c\\\\d e f'
     """
     return (s
         .replace('/*', ' ')