fix signature

[dbarchuk]

When try to create signature got TypeError: LiqPay._make_signature() takes 3 positional arguments but 4 were given because of doubling argument self._private_key)

[aorzh]

Hi @dbarchuk! I've wrote a fork https://github.com/aorzh/liqpay-sdk-python3 because this repo hasn't updates few years. I used this fork in production but it's of course not official. Also, as I see one contributor of current repo already made some changes. Here is his comment: https://github.com/liqpay/sdk-python/issues/17#issuecomment-1867686543

And here is branch where I see actual changes: https://github.com/liqpay/sdk-python/tree/dev_1.1

[dbarchuk]

Hi @dbarchuk! I've wrote a fork https://github.com/aorzh/liqpay-sdk-python3 because this repo hasn't updates few years. I used this fork in production but it's of course not official. Also, as I see one contributor of current repo already made some changes. Here is his comment: #17 (comment)

And here is branch where I see actual changes: https://github.com/liqpay/sdk-python/tree/dev_1.1

I noticed that this repository was last updated three months ago, so I decided to test it. Upon encountering an error, I checked the issues section and found it already reported. I thought perhaps submitting a pull request would be the quickest way to resolve it. Also, I admit I'm too lazy to check all the branches ;)

While it's not a problem to write a custom class instead of using this package (even though it was recommended by the official Liqpay documentation), I just want to ensure it's fixed for the future.