Fix wording in Javadoc of ClientResponse.mutate()

Removed an extra "the".

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientResponse.java

@@ -193,7 +193,7 @@ public interface ClientResponse {
 	String logPrefix();
 
 	/**
-	 * Return a builder to mutate the this response, for example to change
+	 * Return a builder to mutate this response, for example to change
 	 * the status, headers, cookies, and replace or transform the body.
 	 * @return a builder to mutate the request with
 	 * @since 5.3