Remove deprecated endpoints from example project (#40)

The engine APIs are deprecated, and OpenAI will shut them down eventually

Author: TheoKanning

README.md

@@ -47,7 +47,7 @@ CompletionRequest completionRequest = CompletionRequest.builder()
         .model("ada")
         .echo(true)
         .build();
-service.createCompletion( completionRequest).getChoices().forEach(System.out::println);
+service.createCompletion(completionRequest).getChoices().forEach(System.out::println);
 ```
 
 ### Using OpenAiApi Retrofit client

example/src/main/java/example/OpenAiApiExample.java

@@ -2,26 +2,19 @@
 
 import com.theokanning.openai.OpenAiService;
 import com.theokanning.openai.completion.CompletionRequest;
-import com.theokanning.openai.engine.Engine;
 
 class OpenAiApiExample {
     public static void main(String... args) {
         String token = System.getenv("OPENAI_TOKEN");
         OpenAiService service = new OpenAiService(token);
 
-        System.out.println("\nGetting available engines...");
-        service.getEngines().forEach(System.out::println);
-
-        System.out.println("\nGetting ada engine...");
-        Engine ada = service.getEngine("ada");
-        System.out.println(ada);
-
         System.out.println("\nCreating completion...");
         CompletionRequest completionRequest = CompletionRequest.builder()
+                .model("ada")
                 .prompt("Somebody once told me the world is gonna roll me")
                 .echo(true)
                 .user("testing")
                 .build();
-        service.createCompletion("ada", completionRequest).getChoices().forEach(System.out::println);
+        service.createCompletion(completionRequest).getChoices().forEach(System.out::println);
     }
 }