MM-61484 - Deleting scheduled posts when permanently deleting a user (#29152)

* Deleting scheduled posts when permanently deleting a user

* Updated tests

* CI

* Testing CI

* Restored a test change

* Skipping flaky test

server/channels/store/store.go

@@ -1065,6 +1065,7 @@ type ScheduledPostStore interface {
 	UpdatedScheduledPost(scheduledPost *model.ScheduledPost) error
 	Get(scheduledPostId string) (*model.ScheduledPost, error)
 	UpdateOldScheduledPosts(beforeTime int64) error
+	PermanentDeleteByUser(userId string) error
 }
 
 // ChannelSearchOpts contains options for searching channels.