fix error in app.yml

Signed-off-by: Sebastian Schüpbach <sebastian.schuepbach@unibas.ch>

src/main/resources/app.yml

+app:
+  topicTransactionsRecords: ${TOPIC_TRANSACTIONS_RECORDS}
+  topicTransactionsRecordSets: ${TOPIC_TRANSACTIONS_RECORD_SETS}
+  topicTransactionsInstitutions: ${TOPIC_TRANSACTIONS_INSTITUTIONS}
 kafka:
-  app:
-    topicTransactionsRecords: ${TOPIC_TRANSACTIONS_RECORDS}
-    topicTransactionsRecordSets: ${TOPIC_TRANSACTIONS_RECORD_SETS}
-    topicTransactionsInstitutions: ${TOPIC_TRANSACTIONS_INSTITUTIONS}
   streams:
     bootstrap.servers: ${KAFKA_BOOTSTRAP_SERVERS:?system}
     application.id: ${APPLICATION_ID:?system}