fix embedding_model_name not work

[ArnoChenFx]

[!IMPORTANT] Fixes issue in zep_graphiti.py where embedding_model_name was not being set in get_graphiti().

• Behavior:
  • Fixes issue where embedding_model_name was not being set in get_graphiti() in zep_graphiti.py.
  • Adds condition to set client.embedder.config.embedding_model if settings.embedding_model_name is provided.

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