refactor: fix DeepSeekChatModel initialization to use builder pattern (#4421)

Auto-cherry-pick to 1.0.x Fixes #4421 Signed-off-by: fatebug <1339524041@qq.com>

Author: fatebugs

spring-ai-docs/src/main/antora/modules/ROOT/pages/api/chat/deepseek-chat.adoc

@@ -313,14 +313,18 @@ Next, create a `DeepSeekChatModel` and use it for text generation:
 
 [source,java]
 ----
-var deepSeekApi = new DeepSeekApi(System.getenv("DEEPSEEK_API_KEY"));
-
-var chatModel = new DeepSeekChatModel(deepSeekApi, DeepSeekChatOptions.builder()
- .withModel(DeepSeekApi.ChatModel.DEEPSEEK_CHAT.getValue())
- .withTemperature(0.4f)
- .withMaxTokens(200)
- .build());
-
+DeepSeekApi deepSeekApi = DeepSeekApi.builder()
+ .apiKey(System.getenv("DEEPSEEK_API_KEY"))
+ .build();
+DeepSeekChatOptions options = DeepSeekChatOptions.builder()
+ .model(DeepSeekApi.ChatModel.DEEPSEEK_CHAT.getValue())
+ .temperature(0.4)
+ .maxTokens(200)
+ .build();
+DeepSeekChatModel chatModel = DeepSeekChatModel.builder()
+ .deepSeekApi(deepSeekApi)
+ .defaultOptions(options)
+ .build();
 ChatResponse response = chatModel.call(
  new Prompt("Generate the names of 5 famous pirates."));