fix: no events with case as subject

the sub claim refers to the subject of the SET. previously we had events whose subject is the case (case-close-event).

since we no longer have this event, the case subject is no longer needed.

• Release as 1.2.0-rc2
• Copy to Zustelldienst as 1.2.0-rc2. Done @ https://git.fitko.de/fit-connect/zustelldienst/-/commit/6db8fa52d7c184c0a5cee134fd86c875404c8e48