[PATCH] Remove TZ entry from postgres CLI doc page.

Hi,

Please find attached a patch to the postgres command line
documentation page doc/src/sgml/ref/postgres-ref.sgml that removes the
"TZ" entry from the "Environment" section. If I've understood it
correctly, since ca4af308 TZ can be looked at when you run initdb, but
is not looked at when the server is started.

I am using Test::PostgreSQL to create a test database; it empties the
postgresql.conf created by initdb and is then therefore not using the
correct timezone, and it took me a while to work out what was
happening and why I couldn't use TZ when starting the database.

ATB,
Matthew