The error message you are encountering indicates that the Azure Recovery Services vault within your resource group 'learn-file-sync-rg' cannot be deleted. This is likely because there are still dependencies or protected items within the vault that need to be addressed before the vault and subsequently, the resource group can be deleted. Here's what you should do to resolve this issue: Cancel Protected Items: If the vault contains any backups or items that are still being protected, you will need to cancel the protection first. This could mean stopping any backup jobs and deleting backup data, or disabling any replication settings for Site Recovery.
Soft Delete Feature: Azure Recovery Services vaults have a soft delete feature, which retains backup data for a period of time after deletion as a protective measure. If this feature is enabled, you must wait for the soft delete period to expire before the vault can be deleted.
Remove Dependencies - This could include policies or other resources that are still linked to the vault.
Delete Vault: Once all protected items are removed and dependencies are cleared, you should be able to delete the vault from the Azure portal or using Azure CLI or PowerShell commands.
After successfully deleting the vault, you should then be able to delete the resource group itself.