[CI] Reorganize stage-b 1-GPU tests for 5090 compatibility (#16826)

test/registered/layers/mamba/test_mamba2_mixer.py

@@ -1,7 +1,3 @@
-from sglang.test.ci.ci_register import register_cuda_ci
-
-register_cuda_ci(est_time=50, suite="stage-b-test-large-2-gpu")
-
 # Adapted from https://github.com/vllm-project/vllm/blob/2c58742dff8613a3bd7496f2008ce927e18d38d1/tests/kernels/mamba/test_mamba_mixer2.py
 
 
@@ -17,6 +13,9 @@ from sglang.srt.distributed.parallel_state import (
     init_distributed_environment,
     initialize_model_parallel,
 )
+from sglang.test.ci.ci_register import register_cuda_ci
+
+register_cuda_ci(est_time=50, suite="stage-b-test-large-2-gpu")
 
 NUM_GPUS = 2