(AzureCXP) Fixing Typo

Based on customer feedback on below GitHub thread 

https://github.com/MicrosoftDocs/azure-docs/issues/55797

Author: BharathNimmala-MSFT

articles/backup/backup-azure-backup-faq.md

@@ -203,7 +203,7 @@ Yes. The data in Azure is encrypted-at-rest.
 
 Microsoft does not decrypt the backup data at any point.
 
-### What is the minimum length of encryption the key used to encrypt backup data?
+### What is the minimum length of the encryption key used to encrypt backup data?
 
 The encryption key should be at least 16 characters when you are using Azure backup agent. For Azure VMs, there is no limit to length of keys used by Azure KeyVault.