fix: ModelBuilder not passing HF_TOKEN to model.

[makungaj1]

Issue #, if available:

Description of changes:
Fixes:

• ModelBuilder JS Builder not passing HF_TOKEN down to model.
• ModelBuilder build issue with model object.

Testing done:
Tested with this public notebook.

model_builder = ModelBuilder(
    model=target_model_id,
    env_vars={
        "HUGGING_FACE_HUB_TOKEN": hf_hub_token
    },
    schema_builder=SchemaBuilder(sample_input, sample_output),
    sagemaker_session=sagemaker_session,
    role_arn=my_role,
)
optimized_model = model_builder.optimize(
   instance_type="ml.inf2.8xlarge",
   compilation_config={
          "OverrideEnvironment": {
            "OPTION_TENSOR_PARALLEL_DEGREE": "2",
            "OPTION_N_POSITIONS": "8192",
            "OPTION_DTYPE": "fp16",
            "OPTION_ROLLING_BATCH": "auto",
            "OPTION_MAX_ROLLING_BATCH_SIZE": "4",
            "OPTION_NEURON_OPTIMIZE_LEVEL": "2",
         }
   },
   output_path=f"s3://{out_put_bucket}/{uuid.uuid4().hex}/"
)
predictor = optimized_model.deploy(initial_instance_count=1)
predictor.predict(sample_input)
predictor.delete_model()
predictor.delete_endpoint()

model_builder = ModelBuilder(
    model="meta-textgeneration-llama-3-70b",
    schema_builder=SchemaBuilder(sample_input, sample_output),
    sagemaker_session=sagemaker_session,
    role_arn=my_role,
)
model_builder.display_benchmark_metrics()
model_builder.set_deployment_config("lmi-optimized", "ml.p5.48xlarge")

optimized_model = model_builder.optimize(
    accept_eula=True,
    speculative_decoding_config={
        "ModelSource": draft_model_s3_uri
    },
    env_vars={
        "HF_TOKEN": hf_hub_token # verified that HF token was passed correctly
    },
)

predictor = optimized_model.deploy(initial_instance_count=1)
predictor.predict(sample_input)
predictor.delete_model()
predictor.delete_endpoint()

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• I have read the CONTRIBUTING doc
• I certify that the changes I am introducing will be backward compatible, and I have discussed concerns about this, if any, with the Python SDK team
• I used the commit message format described in CONTRIBUTING
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• I have updated any necessary documentation, including READMEs and API docs (if appropriate)

Tests

• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added unit and/or integration tests as appropriate to ensure backward compatibility of the changes
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