pgsql: CREATE POLICY expression -> using_expression

CREATE POLICY expression -> using_expression

The syntax for CREATE POLICY simply used "expression" for the USING
expression, while the WITH CHECK expression was "check_expression".
Given that we have two expressions, it's sensible to explcitly name both
to maintain clarity.

This patch simply changes the generic "expression" to be
"using_expression".

Pointed out by Peter Geoghegan.

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/bb541812b8f67ae0341fa76fe3bb60f58671b8c7

Modified Files
--------------
doc/src/sgml/ref/create_policy.sgml |    4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)