Module-level `__annotations__` variable is flagged as undefined

To repro, run mypy on the following:

```python
print(__annotations__)
```

```
test.py:1: error: Name '__annotations__' is not defined
Found 1 error in 1 file (checked 1 source file)
```

A pyright user recently noted [the same issue in pyright](https://github.com/microsoft/pylance-release/issues/1161), which I have fixed. 