Fix HermesBackupWorker intervals

[SigismundSchlomo]

Why

Typo in field name led to incorrect work of HermesBackupWorker. WorkInterval was undefined and backup was executed only once with initialization of HermesBackupWorker, because timeLeft in PeriodicWorker was equal NaN.

What

• Write field name correctly

Checklist:

• [ ] Code follows the style guidelines
• [ ] Documentation updated
• [ ] Corner cases evaluated and handled
• [ ] Automatic tests added/update
• [ ] Automatic tests pass
• [ ] Software runs (locally or hosted)
• [ ] Sanity check passed
• [ ] Self-review passed