Comment out onboarding dualtor (#20567)

Why I did it
As all dualtor test scripts are stable, we have moved them to dualtor PR checker. We don't need onboarding dualtor PR checker anymore. So in this PR, we comment out the onboarding dualtor PR checker.

azure-pipelines.yml

@@ -295,22 +295,22 @@ stages:
           MGMT_BRANCH: $(BUILD_BRANCH)
           TEST_SET: onboarding_t1
 
-  - job: onboarding_elastictest_dualtor
-    displayName: "onboarding dualtor testcases by Elastictest - optional"
-    timeoutInMinutes: 240
-    continueOnError: true
-    pool: sonic-ubuntu-1c
-    steps:
-      - template: .azure-pipelines/run-test-elastictest-template.yml@sonic-mgmt
-        parameters:
-          TOPOLOGY: dualtor
-          STOP_ON_FAILURE: "False"
-          RETRY_TIMES: 0
-          MIN_WORKER: $(T0_DUALTOR_INSTANCE_NUM)
-          MAX_WORKER: $(T0_DUALTOR_INSTANCE_NUM)
-          KVM_IMAGE_BRANCH: $(BUILD_BRANCH)
-          MGMT_BRANCH: $(BUILD_BRANCH)
-          TEST_SET: onboarding_dualtor
+#  - job: onboarding_elastictest_dualtor
+#    displayName: "onboarding dualtor testcases by Elastictest - optional"
+#    timeoutInMinutes: 240
+#    continueOnError: true
+#    pool: sonic-ubuntu-1c
+#    steps:
+#      - template: .azure-pipelines/run-test-elastictest-template.yml@sonic-mgmt
+#        parameters:
+#          TOPOLOGY: dualtor
+#          STOP_ON_FAILURE: "False"
+#          RETRY_TIMES: 0
+#          MIN_WORKER: $(T0_DUALTOR_INSTANCE_NUM)
+#          MAX_WORKER: $(T0_DUALTOR_INSTANCE_NUM)
+#          KVM_IMAGE_BRANCH: $(BUILD_BRANCH)
+#          MGMT_BRANCH: $(BUILD_BRANCH)
+#          TEST_SET: onboarding_dualtor
 
 #  - job: wan_elastictest
 #    displayName: "kvmtest-wan by Elastictest"