bug(scripts/megatron): hardcoded TP size for SimAI AIOB workload generator

Creating this issue to track: https://github.com/aliyun/aicb/pull/41#issuecomment-3284765622

> `megatron_workload_with_aiob.sh` script for DeepSeek(617&236&16) hardcodes `tensor_model_parallel_size=1` (like [here](https://github.com/parthpower/aicb/blob/deepseek-workload/scripts/megatron_workload_with_aiob.sh#L185)), overriding user settings.