Update runner label for MetaX C550 configuration

Author: mingjiang180

.github/configs/metax.yml

@@ -11,7 +11,7 @@ ci_train_image: harbor.baai.ac.cn/flagscale/megatron-lm-with-te:202603231839
 ci_inference_image: harbor.baai.ac.cn/flagscale/megatron-lm-with-te:202603231839
 
 # Runner labels for MetaX C550 hardware
-runner_labels: ["mx-flagscale-test-v1"]
+runner_labels: ["mx-flagscale-test-v2"]
 
 # Container volumes (hardware-specific paths)
 container_volumes: