fix: example for destination-list

spec/examples/destination-list.yml

 value:
-  - destinationId: de735e92-8ced-4298-a021-5f4aa124cc47
-    schemas:
-      - mimeType: application/json
-        schemaSource: none
-    callback: 'https://example.com/api-callback2'
-  - destinationId: 2f59b8c6-3206-4734-aa21-a7b2a4d92f7a
-    schemas:
-      - mimeType: application/xml
-        schemaSource: none
-      - mimeType: application/json
-        schemaSource: none
-      - mimeType: application/xml
-        schemaSource: fim
-        schemaId: S99000001V1.0
-    callback: 'https://example.com/api-callback3'
\ No newline at end of file
+  destinations:
+    - destinationId: de735e92-8ced-4298-a021-5f4aa124cc47
+      schemas:
+        - mimeType: application/json
+          schemaSource: none
+      callback: 'https://example.com/api-callback2'
+    - destinationId: 2f59b8c6-3206-4734-aa21-a7b2a4d92f7a
+      schemas:
+        - mimeType: application/xml
+          schemaSource: none
+        - mimeType: application/json
+          schemaSource: none
+        - mimeType: application/xml
+          schemaSource: fim
+          schemaId: S99000001V1.0
+      callback: 'https://example.com/api-callback3'