[QA] add tests for new notification feature

[nirajacharya2]

need to extend tests for notification

https://github.com/owncloud/web/blob/master/tests/e2e/cucumber/features/user-settings/notifications.feature

• disable the notifications [tests-only][full-ci] added test for disabling notifications #12189
• check notification with different interval: (for email notification related test, they are covered in the API tests)

[PrajwolAmatya]

The email nofitications for with different interval are mostly covered via API tests. Also, expiring the share via UI seems to be not possible. With completion of PR #12189, marking this issue as completed.