use 'materialized_view' instead of 'materializedview'

[neverchanje]

https://docs.getdbt.com/blog/announcing-materialized-views dbt newly supports the materialized_view model in dbt-postgres.

{{
config(
     materialized='materialized_view',
)
}}

We should maintain the compatibility with other systems.

[chenzl25]

I know dbt 1.6 use materialized_view instead of materializedview, but we are using 1.5 right now. We will change it to materialized_view after we successfully bump dbt core to 1.6