docs/library: Consistently use admonitions for CPython differences.

docs/library/usocket.rst

@@ -171,9 +171,10 @@ Methods
        The socket must be in blocking mode; it can have a timeout, but the file object’s internal buffer
        may end up in a inconsistent state if a timeout occurs.
 
-       .. note::
+       .. admonition:: Difference to CPython
+          :class: attention
 
-          **CPython difference:** closing the file object returned by makefile() WILL close the 
+          Closing the file object returned by makefile() WILL close the
           original socket as well.
 
     .. method:: socket.read(size)

docs/library/utime.rst

@@ -100,9 +100,10 @@ Functions
    if you need calendar time, ``localtime()`` without argument is the best possibility
    to get it.
 
-   .. note::
+   .. admonition:: Difference to CPython
+      :class: attention
 
-      **CPython difference:** In CPython, this function returns number of
+      In CPython, this function returns number of
       seconds since Unix epoch, 1970-01-01 00:00 UTC, as a floating-point,
       usually having microsecond precision. With MicroPython, only Unix port
       uses the same reference point, and if floating-point precision allows,