[API] Inclui endpoint DELETE p/ questão

- [x] corrigir PATCH em /exams/:examId/groups/:groupId do valor esperado na request de array de Group para somente um Group;
- [x] criar DELETE para /exams/:examId/questions/:questionId
- [x] alterar esquema da questão para apresentar `statement` não objetificado

Api/Competition.Adm.API.yaml

@@ -297,7 +297,16 @@ paths:
         required: true
         schema:
           format: int32
-          type: integer  
+          type: integer
+          
+    delete:
+      tags:
+        - exams
+      summary: Delete a question group of a exam
+      description: Delete a question group of a exam.
+      responses:
+        '200':
+          description: 'Successfully deleted'
   /exams/{examId}/groups:
     get:
       tags:
@@ -366,8 +375,7 @@ paths:
             schema:
               type: array
               items:
-                oneOf:
-                  - $ref: 'https://gitlab.dev.evologica.com.br/Competify/Docs/raw/master/Api/components/schemas.yaml/#/QuestionGroup'
+                $ref: 'https://gitlab.dev.evologica.com.br/Competify/Docs/raw/master/Api/components/schemas.yaml/#/QuestionGroup'
         required: true
       responses:
         '200':
@@ -375,10 +383,7 @@ paths:
           content:
             application/json:
               schema:
-                type: array
-                items:
-                  oneOf:
-                    - $ref: 'https://gitlab.dev.evologica.com.br/Competify/Docs/raw/master/Api/components/schemas.yaml/#/QuestionGroup'
+                $ref: 'https://gitlab.dev.evologica.com.br/Competify/Docs/raw/master/Api/components/schemas.yaml/#/QuestionGroup'
     delete:
       tags:
         - exams

Api/components/schemas/Exam.yaml

@@ -36,7 +36,7 @@ Question:
         - SUBJECTIVE
         - OBJECTIVE
     statement:
-      $ref: '#/QuestionStatement'
+      type: string
     id:
       description: object identifier of this Question
       type: integer