[4.1.x] Described Article-Reporter relationship in many-to-one topic.

Backport of 8e93fc561e from main

docs/topics/db/examples/many_to_one.txt

@@ -2,7 +2,10 @@
 Many-to-one relationships
 =========================
 
-To define a many-to-one relationship, use :class:`~django.db.models.ForeignKey`::
+To define a many-to-one relationship, use :class:`~django.db.models.ForeignKey`.
+
+In this example, a ``Reporter`` can be associated with many ``Article``
+objects, but an ``Article`` can only have one ``Reporter`` object::
 
     from django.db import models