[ROCm] [CI] Reduce Resource of two test groups (#34059)

Signed-off-by: tjtanaa <tunjian.tan@embeddedllm.com>

.buildkite/test-amd.yaml

@@ -754,7 +754,7 @@ steps:
 - label: Benchmarks # 11min
   timeout_in_minutes: 20
   mirror_hardwares: [amdexperimental, amdproduction]
-  agent_pool: mi325_8
+  agent_pool: mi325_1
   # grade: Blocking
   working_dir: "/vllm-workspace/.buildkite"
   source_file_dependencies:
@@ -765,7 +765,7 @@ steps:
 - label: Benchmarks CLI Test # 7min
   timeout_in_minutes: 20
   mirror_hardwares: [amdexperimental, amdproduction]
-  agent_pool: mi325_8
+  agent_pool: mi325_1
   # grade: Blocking
   source_file_dependencies:
   - vllm/