Docs: Replace code.code with code.authorizationCode (attempt 2)

[menewman]

Summary

Now, the documentation for model methods getAuthorizationCode and revokeAuthorizationCode consistently refer to code.authorizationCode rather than code.code.

Linked issue

Closes #216.

Involved parts of the project

Documentation only -- specifically for revokeAuthorizationCode and getAuthorizationCode.

Added tests?

N/A

OAuth2 standard

N/A

Reproduction

N/A

[menewman]

@jankapunkt - Hopefully this one is a bit easier to review! Thank you 🙂