Doc: fix missing mention of procedure OUT parameters.
Small oversight in commit
@@ -1959,7 +1959,8 @@ SELECT * FROM get_available_flightid(CURRENT_DATE);
or <command>DO</command> block can call a procedure
using <command>CALL</command>. Output parameters are handled
differently from the way that <command>CALL</command> works in plain
- SQL. Each <literal>INOUT</literal> parameter of the procedure must
+ SQL. Each <literal>OUT</literal> or <literal>INOUT</literal>
+ parameter of the procedure must
correspond to a variable in the <command>CALL</command> statement, and
whatever the procedure returns is assigned back to that variable after
it returns. For example:
