remove grant usage on redshift permissions

this pr removes the `grant usage on database database_name to user_name;` command in the redshift database permissions page. raised with @mikealfare [in internal slack](https://dbt-labs.slack.com/archives/C067EUS2D7S/p1736358281678169)

Resolves #6738

website/docs/reference/database-permissions/redshift-permissions.md

@@ -12,7 +12,6 @@ The following example provides you with the SQL statements you can use to manage
 
 
 ```
-grant usage on database database_name to user_name;
 grant create schema on database database_name to user_name;
 grant usage on schema database.schema_name to user_name;
 grant create table on schema database.schema_name to user_name;
@@ -22,4 +21,6 @@ grant select on all tables in database database_name to user_name;
 grant select on all views in database database_name to user_name;
 ```
 
+To connect to the database, confirm with an admin that your user role or group has been added to the database.
+
 Check out the [official documentation](https://docs.aws.amazon.com/redshift/latest/dg/r_GRANT.html) for more information.