Mention Apple’s February 2021 authentication requirement in Continuous Integration docs

[sonicdoe]

From Apple’s support article on two-factor authentication:

Starting February 2021, two-factor authentication or two-step verification will be required for all users to sign in to App Store Connect.

The Continuous Integration page only mentions the older February 2019 requirement:

Note: Apple announced that as of February 27th 2019, it is enforcing 2-factor authentication on developer Apple IDs with the "Account Holder" role.

I’d suggest to update this section to mention the February 2021 requirement (and drop the old note).

[max-ott]

Fastlane is open source. Please open a pull request and change the docs in it.

[sonicdoe]

As I’ve said in #18123, I hope my post didn’t come across as dismissive. As with that question, this one was also resolved by fastlane/docs#1032 🙌