Outdated example syntax in Constraint docs

https://orm.drizzle.team/docs/indexes-constraints

The examples in the docs for table constraints (unique, check, etc) show an object return syntax for the extraConfig callback:

```ts
export const userNulls = pgTable('user_nulls_example', {
id: integer('id').unique("custom_name", { nulls: 'not distinct' }),
}, (t) => ({
unq: unique().on(t.id).nullsNotDistinct()
}));
```

looks like that syntax was deprecated [by a commit for RLS](https://github.com/drizzle-team/drizzle-orm/blob/05e88e44857b0f6017be1e2d1d5ebee53c7336ca/drizzle-orm/src/pg-core/table.ts) about a month ago & now it expects an array return:

```ts
export const userNulls = pgTable('user_nulls_example', {
id: integer('id').unique("custom_name", { nulls: 'not distinct' }),
}, (t) => [
unique().on(t.id).nullsNotDistinct()
]);
```

would also be helpful to add a note or something for this change since it's breaking from how constraints used to work in drizzle

thanks!