Fix: Incorrect arguments in README

[elpnt]

Fixed incorrect arguments for useSignInWithEmailAndPassword hook

[chrisbianca]

@elpnt thanks for this, but I think you have misinterpreted the function.

The hook returns a function that you pass the username and password to, so you don't need to pass the username and password to the hook itself

[elpnt]

@chrisbianca I know the function requires only the Firebase Auth instance, but the username and password are passed to in the short example code.

https://github.com/CSFrequency/react-firebase-hooks/blob/ef8e19ea9492c610e4b44d2a06f295719fff7982/auth/README.md?plain=1#L162-L169

[chrisbianca]

@elpnt sorry, that will teach me to try and view a PR on my phone and get confused as to which way round the change is! Good catch, I will merge now!