#20135: FAQ entry for list mutation. (See also 6375bf34fff6.)

I accidentally committed this in 6375bf34fff6; this changeset addresses the
last review comments on the patch.

This is a perennial question and something someone opens a ticket for probably
every other month or so, so I'm surprised we didn't already have a FAQ entry
for it.

The original patch was written by M. Votz, refined first by Ezio Melotti and
further refined by me.

Doc/faq/programming.rst

@@ -473,7 +473,7 @@ There are two factors that produce this result:
 
 After the call to :meth:`~list.append`, the content of the mutable object has
 changed from ``[]`` to ``[10]``.  Since both the variables refer to the same
-object, accessing either one of them accesses the modified value ``[10]``.
+object, using either name accesses the modified value ``[10]``.
 
 If we instead assign an immutable object to ``x``::