[BUG] Self-Scheduled Assignments are sending expiration notifications

[sadsfae]

We shouldn't be sending expiration notifications for self-scheduled assignments because by design there is no way for tenants to extend them.

We might consider sending one a day before expiration as a notice but I'd be fine not sending any - they can look at and track their own reservations via the wiki.

[sadsfae]

self-scheduled assignments are sending the full 7,5,3,1 day expirations when they shouldn't send any (self-scheduled assignments cannot be extended and always expire based on ssm_deadline_day and ssm_deadline_hour per https://github.com/redhat-performance/quads/blob/latest/conf/selfservice.yml#L14

58056   C May 03 RDU2 Scale Lab  (   0) New QUADS Assignment Defined for the Future: cloud02 - 4275
58058   C May 03 RDU2 Scale Lab  (   0) Validation check succeeded for cloud02 / nchhabra / 4275
58059   C May 03 RDU2 Scale Lab  (   0) New QUADS Assignment Allocated - cloud02 4275
58060   C May 03 RDU2 Scale Lab  (   0) QUADS upcoming expiration for cloud02 - 4275
58061   C May 03 RDU2 Scale Lab  (   0) QUADS upcoming expiration for cloud02 - 4275

[grafuls]

https://review.gerrithub.io/c/redhat-performance/quads/+/1214844