fix checkstyle

Author: StefanBratanov

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/tracing/zipkin/ZipkinHttpSenderTests.java

@@ -1,3 +1,19 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package org.springframework.boot.actuate.autoconfigure.tracing.zipkin;
 
 import java.io.IOException;
@@ -92,11 +108,11 @@ private CallbackResult(boolean isSuccess, Throwable error) {
 		}
 
 		public boolean isSuccess() {
-			return isSuccess;
+			return this.isSuccess;
 		}
 
 		public Throwable getError() {
-			return error;
+			return this.error;
 		}
 
 	}