Change test pipeline to run in eastus2 (#16950)

- The test resources rely on an ASA account, which isn't available in westus2, the default region.  So, i've adjusted the region to eastus2.

Author: craigktreasure

sdk/mixedreality/tests.yml

@@ -6,6 +6,7 @@ stages:
       AllocateResourceGroup: false
       ServiceDirectory: mixedreality
       DeployArmTemplate: true
+      Location: eastus2
       EnvVars:
         AZURE_CLIENT_ID: $(aad-azure-sdk-test-client-id)
         AZURE_CLIENT_SECRET: $(aad-azure-sdk-test-client-secret)