raise atol for MT5OnnxConfig (#18560)

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

src/transformers/models/mt5/configuration_mt5.py

@@ -147,9 +147,9 @@ class MT5Config(PretrainedConfig):
         return self.num_layers
 
 
-# Copied from transformers.models.t5.configuration_t5.T5OnnxConfig
 class MT5OnnxConfig(OnnxSeq2SeqConfigWithPast):
     @property
+    # Copied from transformers.models.t5.configuration_t5.T5OnnxConfig.inputs
     def inputs(self) -> Mapping[str, Mapping[int, str]]:
         common_inputs = {
             "input_ids": {0: "batch", 1: "encoder_sequence"},
@@ -169,5 +169,10 @@ class MT5OnnxConfig(OnnxSeq2SeqConfigWithPast):
         return common_inputs
 
     @property
+    # Copied from transformers.models.t5.configuration_t5.T5OnnxConfig.default_onnx_opset
     def default_onnx_opset(self) -> int:
         return 13
+
+    @property
+    def atol_for_validation(self) -> float:
+        return 5e-4