bpo-34804: [doc] Rephrase section on side effects in functional.rst for clarity (GH-27989)

Co-authored-by: Łukasz Langa <[email protected]>

Author: DonnaDia

Doc/howto/functional.rst

@@ -65,11 +65,10 @@ output must only depend on its input.
 
 Some languages are very strict about purity and don't even have assignment
 statements such as ``a=3`` or ``c = a + b``, but it's difficult to avoid all
-side effects.  Printing to the screen or writing to a disk file are side
-effects, for example.  For example, in Python a call to the :func:`print` or
-:func:`time.sleep` function both return no useful value; they're only called for
-their side effects of sending some text to the screen or pausing execution for a
-second.
+side effects, such as printing to the screen or writing to a disk file. Another
+example is a call to the :func:`print` or :func:`time.sleep` function, neither
+of which returns a useful value. Both are called only for their side effects
+of sending some text to the screen or pausing execution for a second.
 
 Python programs written in functional style usually won't go to the extreme of
 avoiding all I/O or all assignments; instead, they'll provide a