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.