[ROCm][CI] Fix AMD CI pipeline upload rejected by an invalid block-step key (#57375)

Signed-off-by: Matthew Wong <Matthew.Wong2@amd.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

.buildkite/test-amd.yaml

@@ -2414,7 +2414,7 @@ steps:
   - pytest -v -s entrypoints/serve/instrumentator/test_uds.py
   - pytest -v -s v1/sample/test_logprobs_e2e.py -k "test_prompt_logprobs_e2e_server"
 
-- label: ":amd: (MI300) Rust Frontend Serve/Admin Coverage"
+- label: ":amd: (MI300) Rust Frontend Serve-Admin Coverage"
   timeout_in_minutes: 30
   mirror_hardwares: [amdexperimental, amdproduction, amdgfx942nightly, amdmi300]
   dind: false