[doc] update lora doc

[reidliu41]

update the lora doc for jq install tips, and API response description.

vllm serve meta-llama/Llama-2-7b-hf --enable-lora --lora-modules sql-lora=/home/xx/sql-lora/
INFO 05-10 10:46:14 [serving_models.py:185] Loaded new LoRA adapter: name 'sql_adapter', path '/home/xx/sql-lora'
INFO:     127.0.0.1:55020 - "POST /v1/load_lora_adapter HTTP/1.1" 200 OK
INFO 05-10 10:56:49 [serving_models.py:202] Removed LoRA adapter: name 'sql_adapter'
INFO:     127.0.0.1:54752 - "POST /v1/unload_lora_adapter HTTP/1.1" 200 OK


$ curl -X POST http://localhost:8000/v1/load_lora_adapter -H "Content-Type: application/json" -d '{
    "lora_name": "sql_adapter",
    "lora_path": "/home/xx/sql-lora"
}'
Success: LoRA adapter 'sql_adapter' added successfully.

$ curl -X POST http://localhost:8000/v1/unload_lora_adapter \
> -H "Content-Type: application/json" \
> -d '{
>     "lora_name": "sql_adapter"
> }'
Success: LoRA adapter 'sql_adapter' removed successfully.

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[jeejeelee]

LGTM