Remove lr scheduler in DeepSpeed config to avoid conflict

[Haoxiang-Wang]

This PR removed the following schduler in DeepSpeed config files.

{
  "scheduler": {
    "type": "WarmupDecayLR",
    "params": {
      "warmup_min_lr": "auto",
      "warmup_max_lr": "auto",
      "warmup_num_steps": "auto",
      "warmup_type": "linear",
      "total_num_steps": "auto"
    }
}

The scheduler in DeepSpeed configurations is not necessary because the axolotl package defines its own learning rate scheduler (which is passed to the HuggingFace trainer). In fact, the DeepSpeed scheduler can sometimes cause conflicts. For instance, when lr_scheduler: constant_with_warmup is set in the training YAML file, the actual scheduler is overridden by DeepSpeed's scheduler (which is DeepSpeed's WarmupDecayLR instead of HuggingFace's constant_with_warmup). Removing scheduler from DeepSpeed configurations can resolve this issue.