[3.13] gh-139783: Fix inspect.getsourcelines() for the case when a decorator is followed by a comment or an empty line (GH-139836) (GH-139890)

(cherry picked from commit f4104f5d74b99712253fceb39a4460ee3f7a281c)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>