[hotfix] bump hotline message expiry interval from 3 days to 1 week
- we observed several cases of trying to respond to a hotline message more than 3 days old and not being able to (b/c the hotline message id used to respond to the sender had been destroyed)
- this is sad!
- a week seems like a more reasonable time frame to expect to be able to respond to a message within and does not seem like too long to keep data around without deleting it (it is how long we preserve channels without people using them)
- so: this MR updates the hotline message id deletion job to wait a week isntead of 3 days before deleting hotline ids. (it also updates our privacy policy to reflect that data retention decision)