server : do not get prompt in infill mode (#7286)

* avoid to get prompt in infill mode and embedding mode

* remove embedding mode

* refactor format

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Co-authored-by: wudexiang <wudexiang@bytedance.com>

examples/server/server.cpp

@@ -888,7 +888,7 @@ struct server_context {
         slot.params.input_suffix = json_value(data, "input_suffix", default_params.input_suffix);
 
         // get prompt
-        {
+        if (!task.infill) {
             const auto & prompt = data.find("prompt");
             if (prompt == data.end()) {
                 send_error(task, "Either \"prompt\" or \"messages\" must be provided", ERROR_TYPE_INVALID_REQUEST);