chore: update CI test est_time values (#22565)

Co-authored-by: Cheng Wan <chwan@rice.edu>
Co-authored-by: sglang-bot <sglang-bot@users.noreply.github.com>
Co-authored-by: Cheng Wan <54331508+ch-wan@users.noreply.github.com>

test/registered/layers/mamba/test_mamba2_mixer.py

@@ -15,7 +15,7 @@ from sglang.srt.distributed.parallel_state import (
 )
 from sglang.test.ci.ci_register import register_cuda_ci
 
-register_cuda_ci(est_time=50, suite="stage-b-test-2-gpu-large")
+register_cuda_ci(est_time=28, suite="stage-b-test-2-gpu-large")
 
 NUM_GPUS = 2