ManyToManyField examples are confused about how many Publication objects there are

[Marnanel Thurman]

In ​https://docs.djangoproject.com/en/2.0/topics/db/examples/many_to_many/ , the text says there are two Publication objects ("a couple" and "both"), but the code example creates three, and uses three.

Create a couple of Publications:

>>> p1 = Publication(title='The Python Journal')
>>> p1.save()
>>> p2 = Publication(title='Science News')
>>> p2.save()
>>> p3 = Publication(title='Science Weekly')
>>> p3.save()

[...]

Create another Article, and set it to appear in both Publications:

>>> a2 = Article(headline='NASA uses Python')
>>> a2.save()
>>> a2.publications.add(p1, p2)
>>> a2.publications.add(p3)

[Tim Graham <timograham@…>]

In cef8f6a6:

Fixed #29591 -- Fixed numbering words in docs/topics/db/examples/many_to_many.txt.

[Tim Graham <timograham@…>]

In 9cd6f9c1:

[2.1.x] Fixed #29591 -- Fixed numbering words in docs/topics/db/examples/many_to_many.txt.

Backport of cef8f6a61bc8079fa36cb37a7d411b56869ffe32 from master