Nuke helix arm runs on 3.1 (#15390)

.azure/pipelines/helix-test.yml

@@ -25,23 +25,3 @@ jobs:
     - name: Helix_logs
       path: artifacts/log/
       publishOnError: true
-
-# Build Helix ARM64
-- template: jobs/default-build.yml
-  parameters:
-    jobName: Helix_arm64
-    jobDisplayName: "Tests: Helix ARM64"
-    agentOs: Linux
-    timeoutInMinutes: 240
-    steps:
-    - script: ./restore.sh -ci
-      displayName: Restore
-    - script: ./build.sh -ci --arch arm64 -test --no-build-nodejs -projects $(Build.SourcesDirectory)/eng/helix/helix.proj /p:IsHelixJob=true /p:BuildAllProjects=true /p:BuildNative=true -bl
-      displayName: Run build.sh helix arm64 target
-      env:
-        SYSTEM_ACCESSTOKEN: $(System.AccessToken) # We need to set this env var to publish helix results to Azure Dev Ops
-    installNodeJs: false
-    artifacts:
-    - name: Helix_arm64_logs
-      path: artifacts/logs/
-      publishOnError: true