[PB] As an administrator, I would like to be able to delete all expired events to avoid clutter

[CarolineM]

Priority: 3 Acceptance criteria:

• Events older than 24 hours should not show up on the app.

Story points: Task breakdown:

• Set method to search for all events more than 24 hours old and delete them: https://github.com/CPSC310W2012/Team-01/issues/16
• Automate this to occur daily: https://github.com/CPSC310W2012/Team-01/issues/17