MapTuple(fn) fails if fn has type hints but no default args

```

def test_typed_maptuple(self):
def fn(e1: int, e2: int) -> int:
return e1 * e2

result = [(1, 1), (2, 2)] | beam.MapTuple(fn)
self.assertEqual([2, 4], sorted(result))

```

Fails in getcallargs_forhints_impl_py3 with:
```

> raise TypeCheckError(e)
E apache_beam.typehints.decorators.TypeCheckError: too many
positional arguments

```

Imported from Jira [BEAM-8588](https://issues.apache.org/jira/browse/BEAM-8588). Original Jira may contain additional context.
Reported by: udim.