fix for missing mcore arg
jenkins Addressed in #8113 so closing this
# What does this PR do ?

Mcore refactor introduced an error when trying to merge.
```
Loading distributed checkpoint with TensorStoreLoadShardedStrategy
[NeMo I 2023-12-13 12:13:12 nlp_overrides:752] Model MegatronGPTModel was successfully restored from /workspace/models/nemo_version/llama2-7b.nemo.
Error executing job with overrides: []
Traceback (most recent call last):
  File "/workspace/NeMo/scripts/nlp_language_modeling/merge_lora_weights/merge.py", line 198, in main
    lora_model_cfg = MegatronGPTLoRAModel.restore_from(
TypeError: NLPModel.restore_from() got an unexpected keyword argument 'mcore'
```
This PR is a patch for this error.

**Collection**: [Note which collection this PR will affect]

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