## Description

Attempting to use Celery in a mypy enabled project we found that errors in Celery's type annotations prevent mypy running against our code. Basically this https://stackoverflow.com/questions/68114378/mypy-crashes-due-to-syntax-error-in-underlying-modules situation 

This branch doesn't attempt to fully overhaul the annotations; it just makes it possible to 

```
from celery import Celery
from celery.schedules import crontab
```
successfully.
Correct some mypy errors. ## Description

Attempting to use Celery in a mypy enabled project we found that errors in Celery's type annotations prevent mypy running against our code. Basically this https://stackoverflow.com/questions/68114378/mypy-crashes-due-to-syntax-error-in-underlying-modules situation 

This branch doesn't attempt to fully overhaul the annotations; it just makes it possible to 

```
from celery import Celery
from celery.schedules import crontab
```
successfully.
import celery  # noqa

import celery  # noqa
