docs/differences: Update python_36 now that b2a_base64 accepts newline.

Signed-off-by: Damien George <damien@micropython.org>

docs/differences/python_36.rst

@@ -78,7 +78,7 @@ Changes to built-in modules:
   +--------------------------------------------------------------------------------------------------------------+----------------+
   | `binascii <https://docs.python.org/3.6/whatsnew/3.6.html#binascii>`_                                         |                |
   +--------------------------------------------------------------------------------------------------------------+----------------+
-  | The b2a_base64() function now accepts an optional newline keyword argument to control whether the newline    |                |
+  | The b2a_base64() function now accepts an optional newline keyword argument to control whether the newline    | Completed      |
   | character is appended to the return value                                                                    |                |
   +--------------------------------------------------------------------------------------------------------------+----------------+
   | `cmath <https://docs.python.org/3.6/whatsnew/3.6.html#cmath>`_                                               |                |