📚 Documentation: Update Account API Reference

[choir27]

💭 Description

Update the following in the Account API Reference Docs (https://appwrite.io/docs/references/cloud/client-web/account):

• [x] Create 2FA challenge should be MFA
• [x] Change "Add Authenticator" to "Create Authenticator"
• [x] Change "Create phone verification (confirmation)" to "Update phone verification (confirmation)"

We want to be consistent in using MFA over 2FA and using CRUD verbs for the endpoints.

👀 Have you spent some time to check if this issue has been raised before?

• [X] I checked and didn't find similar issue

🏢 Have you read the Code of Conduct?

• [X] I have read the Code of Conduct