Remove "Trust this device" from Google Authenticator section

Issue in ./help/systems/security-two-factor-authentication-use.md

In the Google Authenticator section, it shows a screencap with a checkbox for 'Trust this device, do not ask again' and states in point 4
"To save the authentication for future logins, select the Trust this device, do not ask again checkbox."

However from 2.4.2 onwards, this was removed and merchants no longer see this option, as implied in this comment on Stack Overflow
https://magento.stackexchange.com/questions/339801/magento-2-4-2-admin-2-factor-auth-not-enabling-trust-this-device

This is confusing merchants who have asked where the setting is on their installation. Please update the screencap and remove point 4.

Open help/systems/security-two-factor-authentication-use.md and locate the Google Authenticator section. Review the existing screencap and step 4 against the documented Adobe Commerce 2.4.2 behavior. Done means the outdated screencap is updated and the instruction to select “Trust this device, do not ask again” is removed.

Written by the indexing model from the issue text.