Remove unused `Dict` import in api_validator.py

## Description
`api_validator.py` line 3 imports `Dict` from `typing`:
```python
from typing import Tuple, Dict
Tuple is used as a return type hint, but Dict is never referenced anywhere in the file. This is dead code.
```

##Proposed Fix

Change the import to from typing import Tuple.

Labels: chore, good first issue