[Communication] - Clean up Environment Variables in test.yml (Azure#18276)

* Update Identity Readme

* Revert Readme

* Cleaning up environment variables in tests.yml

Co-authored-by: Minnie Liu <peiliu@microsoft.com>

Author: minnieliu

sdk/communication/tests.yml

@@ -1,7 +1,7 @@
 trigger: none
 
 parameters:
-  - name: TestPackagesEnabled 
+  - name: TestPackagesEnabled
     type: object
     default:
       - identity
@@ -25,7 +25,6 @@ stages:
         EnvVars:
           AZURE_TEST_RUN_LIVE: 'true'
           AZURE_TENANT_ID: $(aad-azure-sdk-test-tenant-id)
-          AZURE_SUBSCRIPTION_ID: $(acs-subscription-id)
           AZURE_CLIENT_SECRET: $(aad-azure-sdk-test-client-secret)
           AZURE_CLIENT_ID: $(aad-azure-sdk-test-client-id)
           AZURE_COMMUNICATION_SERVICE_CONNECTION_STRING: $(communication-livetest-connection-string)