BUG #13445: 8.15.1 is missleading regarding array dimensionality

The following bug has been logged on the website:

Bug reference:      13445
Logged by:          Brent Douglas
Email address:      brent.n.douglas@gmail.com
PostgreSQL version: 9.4.4
Operating system:   docs only
Description:

Section 8.15.1 is slightly missleading regarding array dimensionality as the
first example and following comment both read like array declarations in
many programming languages where [] is a single dimensional array and [][]
is a two dimensional array while having different semantics.

To make it more obvious that arrays do not have dimensions the section
stating this could be moved before the example table sal_emp.

The words "one-dimensional" and "two-dimensional" in the comment on the
sal_emp example table could also be removed.