feat: Remove submissions/replies list from `GET /cases/<id>` (planning#511)

spec/examples/case/case-replies-item.yaml

-value:
-  replyId: cc0a3671-09ca-4966-af8e-e61d20b37436

spec/examples/case/case-submissions-item.yaml

-value:
-  submissionId: ce75a6b8-d72f-4b94-b09e-af6be35bc2ae

spec/examples/case/case.yaml

 value:
   caseId: e89e107e-ed79-40e6-ad34-4e770f9df263
   destinationId: 879ee109-a690-4db8-ab32-424284184d7d
-  submissions:
-    - submissionId: ce75a6b8-d72f-4b94-b09e-af6be35bc2ae
-  replies:
-    - replyId: cc0a3671-09ca-4966-af8e-e61d20b37436

spec/schemas/case/case-replies-item.yaml

-title: Antwort
-description: Übertragene Antwort innerhalb eines Vorgangs.
-type: object
-properties:
-  replyId:
-    $ref: "../../parameters/replyId.yaml#/schema"
-required:
-  - replyId

spec/schemas/case/case-submissions-item.yaml

-title: Einreichung
-description: Übertragene Einreichung innerhalb eines Vorgangs.
-type: object
-properties:
-  submissionId:
-    $ref: "../../parameters/submissionId.yaml#/schema"
-required:
-  - submissionId

spec/schemas/case/case.yaml

 title: Vorgang
 description: >
   Beschreibt einen Vorgang (`case`).
-  Dieser klammert Einreichungen und Antworten.
 properties:
   caseId:
     $ref: "../../parameters/caseId.yaml#/schema"
   destinationId:
     $ref: "../../parameters/destinationId.yaml#/schema"
-  submissions:
-    type: array
-    items:
-      $ref: "./case-submissions-item.yaml"
-  replies:
-    type: array
-    items:
-      $ref: "./case-replies-item.yaml"
 required:
   - caseId
   - destinationId
-  - submissions
-  - replies

spec/submission-api.yaml

@@ -232,14 +232,10 @@ components:
       $ref: './schemas/event-payload-accept.yaml'
     EventPayloadAccept:
       $ref: './schemas/event-payload-reject.yaml'
-    ActiveCases:
+    Cases:
       $ref: './schemas/case/list-cases.yaml'
     MinimalCase:
       $ref: './schemas/case/case-minimal.yaml'
-    CaseRepliesItem:
-      $ref: './schemas/case/case-replies-item.yaml'
-    CaseSubmissionsItem:
-      $ref: './schemas/case/case-submissions-item.yaml'
 
   examples:
     Submission: