Disable tests and benchmark on S20 phone. (#6331)

The phone is currently offline.
diff --git a/build_tools/buildkite/cmake/android/arm64-v8a/benchmark.yml b/build_tools/buildkite/cmake/android/arm64-v8a/benchmark.yml
index 35181d8..8971cb1 100644
--- a/build_tools/buildkite/cmake/android/arm64-v8a/benchmark.yml
+++ b/build_tools/buildkite/cmake/android/arm64-v8a/benchmark.yml
@@ -45,7 +45,9 @@
     artifact_paths: "mako-*.log"
     timeout_in_minutes: "15"
 
+  # TODO(6330): Skip as the phone is currently offline.
   - label: "benchmark on Galaxy S20 (exynos-990, mali-g77)"
+    skip: "Currently offline"
     commands:
       - "buildkite-agent artifact download --step build model-S20-artifacts.tgz ./"
       - "buildkite-agent artifact download --step build flagfiles.tgz ./"
diff --git a/build_tools/buildkite/cmake/android/arm64-v8a/benchmark2.yml b/build_tools/buildkite/cmake/android/arm64-v8a/benchmark2.yml
index b8793d0..69f7de6 100644
--- a/build_tools/buildkite/cmake/android/arm64-v8a/benchmark2.yml
+++ b/build_tools/buildkite/cmake/android/arm64-v8a/benchmark2.yml
@@ -39,7 +39,9 @@
     artifact_paths: "benchmark-results-pixel-4.json"
     timeout_in_minutes: "30"
 
+  # TODO(6330): Skip as the phone is currently offline.
   - label: "Benchmark on Galaxy S20 (exynos-990, mali-g77)"
+    skip: "Currently offline"
     commands:
       - "buildkite-agent artifact download --step Build benchmark-suites.tgz ./"
       - "buildkite-agent artifact download --step Build iree-android-tools.tgz ./"
diff --git a/build_tools/buildkite/cmake/android/arm64-v8a/pipeline.yml b/build_tools/buildkite/cmake/android/arm64-v8a/pipeline.yml
index 98808a2..b460cfa 100644
--- a/build_tools/buildkite/cmake/android/arm64-v8a/pipeline.yml
+++ b/build_tools/buildkite/cmake/android/arm64-v8a/pipeline.yml
@@ -17,7 +17,9 @@
 
   - wait
 
+  # TODO(6330): Skip as the phone is currently offline.
   - label: "test on Galaxy S20 (exynos-990, mali-g77)"
+    skip: "Currently offline"
     commands:
       - "buildkite-agent artifact download --step build build-artifacts.tgz ./"
       - "tar xzf build-artifacts.tgz"