pgsql: Remove protocol documentation paragraph about environment

Log Message:
-----------
Remove protocol documentation paragraph about environment variable
passing being "covered elsewhere", per Dave Page.

Modified Files:
--------------
pgsql/doc/src/sgml:
protocol.sgml (r1.82 -> r1.83)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/protocol.sgml?r1=1.82&r2=1.83)