tiny psql doc inconsistency

Hello,

While reading the documentation, I noticed an tiny inconsistency at the
end of:

https://www.postgresql.org/docs/devel/static/app-psql.html

testdb=> SELECT first, second, first > 2 AS gt2 FROM my_table;
first | second | ge2
-------+--------+-----
1 | one | f
2 | two | f
3 | three | t
4 | four | t
(4 rows)

The third column name is not consistent with the query, both in 9.6 and
devel documentations.

Attached is a small patch to fix this.

--
Fabien.