Add tips to sync time on iphones for 2FA errors

What does this MR do?

Users sometimes get invalid pin code when providing the 2FA code, which is due to issues with time sync most of the time. But the instructions shown don't apply for iphone users.

Source: https://support.gatehub.net/hc/en-us/articles/360021168354-Time-Synchronization-for-your-2FA-App (Ticket link)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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Security

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