[11.x] Fix double negative in whereNotMorphedTo() query

[owenvoke]

This resolves an issue with the whereNotMorphedTo() method where the query results in a double negative. This changes to a format that resembles the previous logic.

This issue was introduced in a previous PR (see my comment).

Previous Logic (<11.40)

select *
from `posts`
where not (`posts`.`author_type` <=> 'user' and `posts`.`author_id` <=> 1)

Current logic (>=11.40)

select *
from `posts`
where not ((`posts`.`author_type` <=> 'user' and `posts`.`author_id` not in (1)))

Updated logic (this PR)

This logic aligns more with the previous logic, which does not have a double negative.

select *
from `posts`
where not ((`posts`.`author_type` <=> 'user' and `posts`.`author_id` in (1)))