Improve Javadoc of StructuredLoggingJsonMembersCustomizer to sync with the reference

Author: quaff

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/structured/StructuredLoggingJsonMembersCustomizer.java

@@ -24,7 +24,8 @@
  * customize {@link JsonWriter} {@link Members}.
  * <p>
  * An implementation may be provided using the {@code logging.structured.json.customizer}
- * property.
+ * property. Alternatively, implementations may be listed in a
+ * {@code META-INF/spring.factories} file.
  *
  * @param <T> the type being written
  * @author Phillip Webb