Fix mypy: add type parameters to _LenientDict base class

Change `class _LenientDict(dict)` to `class _LenientDict(dict[str, Any])`
to satisfy mypy [type-arg] check.

Made-with: Cursor

fastapi/dependencies/utils.py

@@ -240,7 +240,7 @@ def get_typed_signature(call: Callable[..., Any]) -> inspect.Signature:
     return typed_signature
 
 
-class _LenientDict(dict):
+class _LenientDict(dict[str, Any]):
     """Dict subclass where missing keys resolve to Any.
 
     Used as an eval namespace so that undefined forward references (e.g. a