Remove unused config class from RestClientAutoConfigurationTests

Closes gh-45372

Author: wilkinsona

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/client/RestClientAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -26,7 +26,6 @@
 import org.springframework.boot.ssl.SslBundles;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.web.client.RestClientCustomizer;
-import org.springframework.boot.web.codec.CodecCustomizer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.converter.HttpMessageConverter;
@@ -156,16 +155,6 @@ void restClientWhenHasCustomMessageConvertersShouldHaveMessageConverters() {
 			});
 	}
 
-	@Configuration(proxyBeanMethods = false)
-	static class CodecConfiguration {
-
-		@Bean
-		CodecCustomizer myCodecCustomizer() {
-			return mock(CodecCustomizer.class);
-		}
-
-	}
-
 	@Configuration(proxyBeanMethods = false)
 	static class RestClientCustomizerConfig {