Minor migration notes fix (#1871)
Minor migration notes fix (#1871)

* moving frontend definition to optional part of the Load Balancer define flow

* initial migration notes for v1.2

* migration notes title fix

martinsawicki/azure-sdk-for-java,hovsepm/azure-sdk-for-java,selvasingh/azure-sdk-for-java,navalev/azure-sdk-for-java,selvasingh/azure-sdk-for-java,Azure/azure-sdk-for-java,navalev/azure-sdk-for-java,navalev/azure-sdk-for-java,navalev/azure-sdk-for-java,hovsepm/azure-sdk-for-java,Azure/azure-sdk-for-java,navalev/azure-sdk-for-java,selvasingh/azure-sdk-for-java,martinsawicki/azure-sdk-for-java,hovsepm/azure-sdk-for-java,hovsepm/azure-sdk-for-java,martinsawicki/azure-sdk-for-java,hovsepm/azure-sdk-for-java,Azure/azure-sdk-for-java,Azure/azure-sdk-for-java,Azure/azure-sdk-for-java