add one limit for shir+ssis ir for variable and parameter

Author: RodgeFu

articles/data-factory/self-hosted-integration-runtime-proxy-ssis.md

@@ -85,6 +85,7 @@ The second staging tasks running on your Azure-SSIS IR will not be billed separa
 - Only OLEDB/Flat File Connection Managers and OLEDB/Flat File Sources are currently supported.
 - Only Azure Blob Storage linked services configured with **Account key**/**SAS URI**/**Service Principal** authentication are currently supported.
 - Only Self-Hosted IR provisioned under the same ADF where your Azure-SSIS IR is provisioned is currently supported.
+- SSIS variables and parameters are not supported.
 
 ## Next steps
 Once you configure your Self-Hosted IR as a proxy for your Azure-SSIS IR, you can deploy and run your packages to access data on premises as Execute SSIS Package activities in ADF pipelines, see [Run SSIS packages as Execute SSIS Package activities in ADF pipelines](https://docs.microsoft.com/azure/data-factory/how-to-invoke-ssis-package-ssis-activity).