deleteSessionByIds lambda expression is causing some issues

Summary

delete() (and other JPA Methods such as deleteAllById()) throws an exception if the entity doesn't exist. In or case, we use this to delete labs that no longer exist in core. Problem is that it can stop pages from rendering if the lab doesn't already exist in queue.

See https://sentry.ewi.tudelft.nl/organizations/eip/issues/2714/?project=4&query=is%3Aunresolved as an example.

Possible Fix

Change to a variant which deletes silently.