ci: update azure subscription location

Author: andrueastman

.azure-pipelines/templates/prepare-unsigned-executable-darwin.yaml

@@ -54,8 +54,8 @@ steps:
   - task: AzureKeyVault@2
     displayName: "Azure Key Vault: Get Secrets"
     inputs:
-      azureSubscription: "MicrosofGraphKeyVault connection"
-      KeyVaultName: MicrosofGraphKeyVault
+      azureSubscription: "Federated AKV Managed Identity Connection"
+      KeyVaultName: akv-prod-eastus
       SecretsFilter: "graph-cli-apple-developer-certificate,graph-cli-apple-developer-certificate-password"
     condition: and(succeeded(), eq(variables['IS_ENABLED'], 'true'), eq(variables['SHOULD_SIGN'], 'True'), startsWith(variables['TARGET_RUNTIME'], 'osx'))