[postgres] remove custom #query
[postgres] remove custom #query

The Rails default implementation will do the right thing, only PG had
a custom implementation.

bruceadams/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,jruby/activerecord-jdbc-adapter,bruceadams/activerecord-jdbc-adapter