fix(login): use correct time for isLocked check

[Sjoertjuh]

Description

Fixes #4950

The time given to the isLocked function is an ISO string because of the implementation of the incrementLoginAttempts function, even though it expects milliseconds since epoch. For this reason the isLocked function will never return true.

• [x] I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] I have ~~added~~ fixed tests that prove my fix is effective or that my feature works
• [x] Existing test suite passes locally with my changes
• [x] I have made corresponding changes to the documentation (none)