pythongh-92417: stdtypes docs: shorten discussion of Python 2 differences

Given that 2.7 has now been end-of-life for two and a half years, I don't think we need such a detailed explanation here anymore of the differences between Python 2 and Python 3.

python#92417

Author: AlexWaygood

Doc/library/stdtypes.rst

@@ -2574,14 +2574,10 @@ since it is often more useful than e.g. ``bytes([46, 46, 46])``.  You can
 always convert a bytes object into a list of integers using ``list(b)``.
 
 .. note::
-   For Python 2.x users: In the Python 2.x series, a variety of implicit
-   conversions between 8-bit strings (the closest thing 2.x offers to a
-   built-in binary data type) and Unicode strings were permitted. This was a
-   backwards compatibility workaround to account for the fact that Python
-   originally only supported 8-bit text, and Unicode text was a later
-   addition. In Python 3.x, those implicit conversions are gone - conversions
+   In Python 3.x, conversions
    between 8-bit binary data and Unicode text must be explicit, and bytes and
-   string objects will always compare unequal.
+   string objects will always compare unequal. This differs from the behaviour
+   in Python 2.x.
 
 
 .. _typebytearray: