Remove deprecated APIs (#120)

## Change
This is part of langchain4j/langchain4j#2726

## General checklist
- [ ] There are no breaking changes
- [ ] I have added unit and/or integration tests for my change
- [ ] The tests cover both positive and negative cases
- [x] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [ ] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
- [ ] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)

Author: dliubarskyi

langchain4j-spring-boot-starter/src/test/java/dev/langchain4j/service/spring/mode/automatic/withRetrievalAugmentor/AiServiceWithRetrievalAugmentorApplication.java

@@ -1,6 +1,7 @@
 package dev.langchain4j.service.spring.mode.automatic.withRetrievalAugmentor;
 
 import dev.langchain4j.data.message.UserMessage;
+import dev.langchain4j.rag.AugmentationResult;
 import dev.langchain4j.rag.RetrievalAugmentor;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
@@ -11,7 +12,9 @@ class AiServiceWithRetrievalAugmentorApplication {
 
     @Bean
     RetrievalAugmentor retrievalAugmentor() {
-        return (userMessage, metadata) -> UserMessage.from("My name is Klaus." + userMessage);
+        return augmentationRequest -> AugmentationResult.builder()
+                .chatMessage(UserMessage.from("My name is Klaus." + augmentationRequest.chatMessage()))
+                .build();
     }
 
     public static void main(String[] args) {