Polish test

This test should not rely on a particular content-type as none is
defined on the producing end, not on the requesting end.

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/RequestMappingIntegrationTests.java

@@ -68,7 +68,6 @@ class RequestMappingIntegrationTests extends AbstractRequestMappingIntegrationTe
 		HttpHeaders headers = getRestTemplate().headForHeaders(url);
 		String contentType = headers.getFirst("Content-Type");
 		assertThat(contentType).isNotNull();
-		assertThat(contentType.toLowerCase()).isEqualTo("text/html;charset=utf-8");
 		assertThat(headers.getContentLength()).isEqualTo(3);
 	}