Fix bytes/string confusion in ctypes docs

Author: Alcaro

Doc/library/ctypes.rst

@@ -306,7 +306,7 @@ Since these types are mutable, their value can also be changed afterwards::
 Assigning a new value to instances of the pointer types :class:`c_char_p`,
 :class:`c_wchar_p`, and :class:`c_void_p` changes the *memory location* they
 point to, *not the contents* of the memory block (of course not, because Python
-bytes objects are immutable)::
+string objects are immutable)::
 
    >>> s = "Hello, World"
    >>> c_s = c_wchar_p(s)