fix typos (#1300)

Author: arov00

kafka-demos/kafka-connect-pipeline/postgres-mysql/source-connector.json

@@ -1,8 +1,8 @@
 {
   "connector.class": "io.debezium.connector.postgresql.PostgresConnector",
   "tasks.max": "1",
-  "key.convertor": "org.apache.kafka.connect.json.JsonConverter",
-  "value.convertor": "org.apache.kafka.connect.json.JsonConverter",
+  "key.converter": "org.apache.kafka.connect.json.JsonConverter",
+  "value.converter": "org.apache.kafka.connect.json.JsonConverter",
   "database.hostname": "postgres",
   "database.port": "5432",
   "database.user": "postgres",