update model template (microsoft#432)

Author: EmmaNingMS

mobile/examples/phi-3/android/app/src/main/java/ai/onnxruntime/genai/demo/MainActivity.java

@@ -68,7 +68,7 @@ public void onClick(View v) {
                 }
 
                 String promptQuestion = userMsgEdt.getText().toString();
-                String promptQuestion_formatted = "<|user|>" + promptQuestion + "<|end|><|assistant|>";
+                String promptQuestion_formatted = "<|user|>\n" + promptQuestion + "<|end|>\n<|assistant|>";
                 Log.i("GenAI: prompt question", promptQuestion_formatted);
                 setVisibility();