docs: Update Offset Pagination With SQLAlchemy example

[ames0k0]

Add missing sync_to_thread=False argument
Also fixed the slice method arguments

Description

slice context

# sqlalchemy/sql/util.py
# start=1, stop=3
limit_clause = _offset_or_limit_clause(stop - start)

# sqlite
select * from person limit -2 offset 3;
-- ...

# postgres
select * from person limit -2 offset 3;
-- LIMIT must not be negative

Closes

#4141