Fix TypeError: _check_required_kwargs() in mqtt5_client_builder.new_default_builder

[matsuokashuhei]

Description of changes:

Fixed following error in mqtt5_client_builder.new_default_builder

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/dist-packages/awsiot/mqtt5_client_builder.py", line 632, in new_default_builder
    _check_required_kwargs(kwargs)
TypeError: _check_required_kwargs() takes 0 positional arguments but 1 was given

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[bretambrose]

Thank you for finding this. This was merged in #406