Update README.md

Fix the parameter syntax --load-choices "default_v1"

README.md

@@ -83,7 +83,7 @@ python -m fastdeploy.entrypoints.openai.api_server \
        --port 8180 \
        --metrics-port 8181 \
        --engine-worker-queue-port 8182 \
-       --load_choices "default_v1" \
+       --load-choices "default_v1" \
        --tensor-parallel-size 1 \
        --max-model-len 131072 \
        --reasoning-parser ernie_x1 \