fix ChatModel docs (#2605)

Fixed deprecated getContent() to getText() in ChatModel documentation.

Signed-off-by: jongin <jonginwon1203@gmail.com>

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

@@ -85,7 +85,7 @@ The interface is defined as follows:
 ```java
 public interface Content {
 
-	String getContent();
+	String getText();
 
 	Map<String, Object> getMetadata();
 }