[relay][frontend][pytorch]Fix a bug in the _get_pytorch_value_type function

[liwangshengya]

Fixed a bug in _get_pytorch_value_type(): kind should be used to determine if it is an OptionalType, instead of pt_dtype

[tvm-bot]

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• cc @shingjan, @yelite _{See #10317 for details}

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[masahi]

Thanks, please fix lint.

[liwangshengya]

@masahi I have have corrected the lint.

[masahi]

@tvm-bot rerun