Javadoc refinement (aligned with 5.2.x)

See gh-25509

spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

@@ -285,9 +285,9 @@ private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) th
 	}
 
 	/**
-	 * Return the charset to use for JSON input.
+	 * Determine the charset to use for JSON input.
 	 * <p>By default this is either the charset from the input {@code MediaType}
-	 * or otherwise falling back on {@code UTF-8}.
+	 * or otherwise falling back on {@code UTF-8}. Can be overridden in subclasses.
 	 * @param contentType the content type of the HTTP input message
 	 * @return the charset to use
 	 * @since 5.1.18