Fix test_modeling_mpt typo in model id (#25606)

Fix model id in get_large_model_config on file test_modeling_mpt

tests/models/mpt/test_modeling_mpt.py

@@ -95,7 +95,7 @@ class MptModelTester:
         self.pad_token_id = vocab_size - 1
 
     def get_large_model_config(self):
-        return MptConfig.from_pretrained("mosaicml/mpt-7")
+        return MptConfig.from_pretrained("mosaicml/mpt-7b")
 
     def prepare_config_and_inputs(self, gradient_checkpointing=False):
         input_ids = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)