docs: improve py create a new user

[Shivamkrishnaa]

Improve documentation

Improve python doc of create a new user.

Link

https://supabase.com/docs/reference/python/auth-signup

Describe the problem

• [x] The example snippet to Sign up, Sign up with additional user metadata should have correct arguments.
• [x] Missing example snippet for Sign up with a redirect URL

Describe the improvement

• [x] Changed example snippet converting the dictionary-style into keyword argument auth.sign_up().
• [x] Added example snipped for Sign up with a redirect URL

Additional context

Here's the error I'm getting if I follow the example snippet

[Shivamkrishnaa]

moved to #22152