[webauthn] Use |authData| instead of |aData| and |adata| in RP assertion verification operation

emlun has just created a new issue for https://github.com/w3c/webauthn:

== Use |authData| instead of |aData| and |adata| in RP assertion verification operation ==
As pointed out by @equalsJeffH in https://github.com/w3c/webauthn/pull/849#discussion_r181531468 , the variable name used in [§7.2. Verifying an authentication assertion][assertion] to refer to the authenticator data is inconsistent. All of the following variants appear:

- `authData`
- `aData`
- `adata`

We should change all these to `authData` to be consistent with [§7.1. Registering a new credential][registration].

[assertion]: https://w3c.github.io/webauthn/#verifying-assertion
[registration]: https://w3c.github.io/webauthn/#registering-a-new-credential

Please view or discuss this issue at https://github.com/w3c/webauthn/issues/879 using your GitHub account