not compatible with pydantic.validate_arguments

A function with `Field` parameter wrapped by `pydantic.validate_arguments`, can not been exeuted from the command line.

```py
from datetime import datetime
from pydantic import Field, validate_arguments

@validate_arguments()
def foo(dt: datetime = Field(default_factory=datetime.now)):
print(dt)

if __name__ == '__main__':
import fire
fire.Fire(foo)
```

run this code from command line with raise:

```
Traceback (most recent call last):
File "/home/xxx/repositories/others/test_fire.py", line 12, in
fire.Fire(foo)
File "/home/xxx/.conda/envs/py39/lib/python3.9/site-packages/fire/core.py", line 141, in Fire
component_trace = _Fire(component, args, parsed_flag_args, context, name)
File "/home/xxx/.conda/envs/py39/lib/python3.9/site-packages/fire/core.py", line 466, in _Fire
component, remaining_args = _CallAndUpdateTrace(
File "/home/xxx/.conda/envs/py39/lib/python3.9/site-packages/fire/core.py", line 681, in _CallAndUpdateTrace
component = fn(*varargs, **kwargs)
File "pydantic/decorator.py", line 40, in pydantic.decorator.validate_arguments.validate.wrapper_function
from contextlib import _GeneratorContextManager
File "pydantic/decorator.py", line 133, in pydantic.decorator.ValidatedFunction.call
func.__dict__.update(kw)
File "pydantic/decorator.py", line 130, in pydantic.decorator.ValidatedFunction.init_model_instance
else:
File "pydantic/main.py", line 341, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for Foo
dt
invalid type; expected datetime, string, bytes, int or float (type=type_error)

```