Revert "[CI Failure] Disable B200 tests while runner is broken" (#31750)

Signed-off-by: Michael Goin <mgoin64@gmail.com>

.buildkite/test-pipeline.yaml

@@ -383,7 +383,6 @@ steps:
 - label: V1 Test attention (B200) # 10min
   timeout_in_minutes: 30
   gpu: b200
-  optional: true # TODO(mgoin): disable optional once runner is fixed
   source_file_dependencies:
     - vllm/v1/attention
     - tests/v1/attention
@@ -944,7 +943,6 @@ steps:
   timeout_in_minutes: 30
   working_dir: "/vllm-workspace/"
   gpu: b200
-  optional: true # TODO(mgoin): disable optional once runner is fixed
   source_file_dependencies:
   - csrc/quantization/fp4/
   - csrc/attention/mla/
@@ -986,7 +984,6 @@ steps:
   timeout_in_minutes: 40
   working_dir: "/vllm-workspace/"
   gpu: b200
-  optional: true # TODO(mgoin): disable optional once runner is fixed
   source_file_dependencies:
   - csrc/quantization/fp4/
   - vllm/model_executor/layers/quantization/utils/flashinfer_utils.py
@@ -1054,7 +1051,6 @@ steps:
   timeout_in_minutes: 60
   working_dir: "/vllm-workspace/"
   gpu: b200
-  optional: true # TODO(mgoin): disable optional once runner is fixed
   source_file_dependencies:
   - tests/quantization/test_blackwell_moe.py
   - vllm/model_executor/models/deepseek_v2.py