Fix typo

Closes spring-projectsgh-7026

Author: snicoll

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -5079,7 +5079,7 @@ configure elements of the auto-configuration you can use the `@AutoConfigureJson
 annotation.
 
 Spring Boot includes AssertJ based helpers that work with the JSONassert and JsonPath
-libraries to check that JSON is as expected. The `JacksonHelper`, `GsonHelper` and
+libraries to check that JSON is as expected. The `JacksonTester`, `GsonTester` and
 `BasicJsonTester` classes can be used for Jackson, Gson and Strings respectively. Any
 helper fields on the test class can be `@Autowired` when using `@JsonTest`.