Fix typos in the previous PR commit

spring-cloud-stream-binder-kafka/src/main/java/org/springframework/cloud/stream/binder/kafka/BinderHeaderMapper.java

@@ -48,10 +48,10 @@ import org.springframework.util.MimeType;
 /**
  * Custom header mapper for Apache Kafka. This is identical to the {@link org.springframework.kafka.support.DefaultKafkaHeaderMapper}
  * from spring Kafka. This is provided for addressing some interoperability issues between Spring Cloud Stream 3.0.x
- * and 2.x apps, where mime types passed as rgeular {@MimeType} in the header are not de-serialized properly.
+ * and 2.x apps, where mime types passed as regular {@link MimeType} in the header are not de-serialized properly.
  * Once those concerns are addressed in Spring Kafka, we will deprecate this class and remove it in a future binder release.
  *
- * Most headers in {@link org.springframework.kafka.support.KafkaHeaders} are not mapped on outbound messages.
+ * Most headers in {@link org.springframework.kafka.support.KafkaHeaders} are not mapped onto outbound messages.
  * The exceptions are correlation and reply headers for request/reply
  * messaging.
  * Header types are added to a special header {@link #JSON_TYPES}.

spring-cloud-stream-binder-kafka/src/test/java/org/springframework/cloud/stream/binder/kafka/KafkaBinderTests.java

@@ -515,7 +515,7 @@ public class KafkaBinderTests extends
 
 		Message<?> message = org.springframework.integration.support.MessageBuilder
 				.withPayload("foo")
-				.setHeader("foo", MimeTypeUtils.TEXT_PLAIN.toString()).build();
+				.setHeader("foo", MimeTypeUtils.TEXT_PLAIN).build();
 
 		moduleOutputChannel.send(message);
 		CountDownLatch latch = new CountDownLatch(1);