[ci] Soft fail and disable retry for AMD build image job (#38505)

Signed-off-by: Kevin H. Luu <khluu000@gmail.com>

.buildkite/hardware_tests/amd.yaml

@@ -5,6 +5,7 @@ steps:
     depends_on: []
     device: amd_cpu
     no_plugin: true
+    soft_fail: true
     commands:
     - >
       docker build
@@ -20,11 +21,3 @@ steps:
     - docker push "rocm/vllm-ci:${BUILDKITE_COMMIT}"
     env:
       DOCKER_BUILDKIT: "1"
-    retry:
-      automatic:
-        - exit_status: -1  # Agent was lost
-          limit: 1
-        - exit_status: -10  # Agent was lost
-          limit: 1
-        - exit_status: 1  # Machine occasionally fail
-          limit: 1