BUG #14104: PREPARE document has a missing parameter in one of the examples

The following bug has been logged on the website:

Bug reference:      14104
Logged by:          Hussain Parsaiyan
Email address:      hus787@gmail.com
PostgreSQL version: 9.5.2
Operating system:   MacOSX
Description:

The second example here:
http://www.postgresql.org/docs/9.4/static/sql-prepare.html

```
PREPARE usrrptplan (int) AS
    SELECT * FROM users u, logs l WHERE u.usrid=$1 AND u.usrid=l.usrid
    AND l.date = $2;
EXECUTE usrrptplan(1, current_date);
```

`usrrptplan` should take in too arguments.