Remove hardcoded inp_tokens name in OpenVINO backend

[zhaixuejun1993]

This pull request makes a small change to the GgmlOvDecoder class in ggml-decoder.h, specifically removing a conditional branch that returned the "inp_tokens" input name. This simplifies the get_graph_input_ov_name method by eliminating handling for input tokens.

• Simplification of graph input name resolution:
  • Removed the condition that returns "inp_tokens" for input tensors, so the method no longer handles this input type. (ggml/src/ggml-openvino/ggml-decoder.h)## Overview

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